diff --git a/src/commands/devices.rs b/src/commands/devices.rs
index 53f121b..4095a46 100644
--- a/src/commands/devices.rs
+++ b/src/commands/devices.rs
@@ -60,8 +60,14 @@ pub fn scan_devices() -> Result<()> {
             println!("  - Check kernel log: dmesg | tail -20");
             println!("  - Check USB bus: lsusb | grep -i -E 'ch34|arduino|1a86|2341'");
         }
+        #[cfg(target_os = "windows")]
+        {
+            println!("  - Open Device Manager and check Ports (COM & LPT)");
+            println!("  - Install CH340 driver if needed: https://www.wch-ic.com/downloads/CH341SER_EXE.html");
+            println!("  - Check if the board appears under \"Other devices\" with a warning icon");
+        }
         println!();
     }
 
     Ok(())
-}
+}
\ No newline at end of file
diff --git a/src/commands/doctor.rs b/src/commands/doctor.rs
index f25aa12..0e93039 100644
--- a/src/commands/doctor.rs
+++ b/src/commands/doctor.rs
@@ -43,10 +43,12 @@ pub fn run_diagnostics() -> Result<()> {
     } else {
         println!(
             "{}",
-            "Issues found. Run 'anvil setup' to fix."
+            "Issues found. See instructions below."
                 .bright_yellow()
                 .bold()
         );
+        println!();
+        print_fix_instructions(&health);
     }
     println!();
 
@@ -78,7 +80,7 @@ pub fn check_system_health() -> SystemHealth {
     let cmake_ok = which::which("cmake").is_ok();
 
     // C++ compiler (optional -- for host tests)
-    let cpp_compiler_ok = which::which("g++").is_ok() || which::which("clang++").is_ok();
+    let cpp_compiler_ok = has_cpp_compiler();
 
     // git
     let git_ok = which::which("git").is_ok();
@@ -99,6 +101,20 @@ pub fn check_system_health() -> SystemHealth {
     }
 }
 
+/// Check for a C++ compiler on any platform.
+fn has_cpp_compiler() -> bool {
+    if which::which("g++").is_ok() || which::which("clang++").is_ok() {
+        return true;
+    }
+    #[cfg(windows)]
+    {
+        if which::which("cl").is_ok() {
+            return true;
+        }
+    }
+    false
+}
+
 fn print_diagnostics(health: &SystemHealth) {
     println!("{}", "Required:".bright_yellow().bold());
     println!();
@@ -139,14 +155,23 @@ fn print_diagnostics(health: &SystemHealth) {
     println!("{}", "Optional:".bright_yellow().bold());
     println!();
 
-    // avr-size
+    // avr-size -- installed as part of the avr core, not a separate step
     if health.avr_size_ok {
         println!("  {} avr-size (binary size reporting)", "ok".green());
-    } else {
+    } else if !health.avr_core_ok {
         println!(
             "  {} avr-size  {}",
             "--".bright_black(),
-            "install: sudo apt install gcc-avr".bright_black()
+            "included with arduino:avr core (no separate install)".bright_black()
+        );
+    } else {
+        // Core is installed but avr-size is not on PATH --
+        // this can happen on Windows where the tool is buried
+        // inside the Arduino15 packages directory.
+        println!(
+            "  {} avr-size  {}",
+            "--".bright_black(),
+            hint_avr_size_not_on_path().bright_black()
         );
     }
 
@@ -171,18 +196,18 @@ fn print_diagnostics(health: &SystemHealth) {
         println!(
             "  {} cmake  {}",
             "--".bright_black(),
-            "install: sudo apt install cmake".bright_black()
+            hint_cmake().bright_black()
         );
     }
 
     // C++ compiler
     if health.cpp_compiler_ok {
-        println!("  {} C++ compiler (g++/clang++)", "ok".green());
+        println!("  {} C++ compiler", "ok".green());
     } else {
         println!(
             "  {} C++ compiler  {}",
             "--".bright_black(),
-            "install: sudo apt install g++".bright_black()
+            hint_cpp_compiler().bright_black()
         );
     }
 
@@ -193,7 +218,7 @@ fn print_diagnostics(health: &SystemHealth) {
         println!(
             "  {} git  {}",
             "--".bright_black(),
-            "install: sudo apt install git".bright_black()
+            hint_git().bright_black()
         );
     }
 
@@ -216,6 +241,160 @@ fn print_diagnostics(health: &SystemHealth) {
     }
 }
 
+/// Print step-by-step fix instructions when required items are missing.
+fn print_fix_instructions(health: &SystemHealth) {
+    println!("{}", "How to fix:".bright_cyan().bold());
+    println!();
+
+    let mut step = 1u32;
+
+    if !health.arduino_cli_ok {
+        println!(
+            "  {}. {}",
+            step,
+            "Install arduino-cli:".bright_white().bold()
+        );
+        if cfg!(target_os = "windows") {
+            println!();
+            println!("     Option A -- WinGet (recommended):");
+            println!("       {}", "winget install ArduinoSA.CLI".bright_cyan());
+            println!();
+            println!("     Option B -- Chocolatey:");
+            println!("       {}", "choco install arduino-cli".bright_cyan());
+            println!();
+            println!("     Option C -- Direct download:");
+            println!(
+                "       {}",
+                "https://arduino.github.io/arduino-cli/installation/"
+                    .bright_cyan()
+            );
+        } else if cfg!(target_os = "macos") {
+            println!("       {}", "brew install arduino-cli".bright_cyan());
+        } else {
+            println!();
+            println!("     Option A -- Install script:");
+            println!(
+                "       {}",
+                "curl -fsSL https://raw.githubusercontent.com/arduino/arduino-cli/master/install.sh | sh"
+                    .bright_cyan()
+            );
+            println!(
+                "       {}",
+                "sudo mv bin/arduino-cli /usr/local/bin/".bright_cyan()
+            );
+            println!();
+            println!("     Option B -- Package manager:");
+            println!(
+                "       {}  {}",
+                "sudo apt install arduino-cli".bright_cyan(),
+                "(Debian/Ubuntu)".bright_black()
+            );
+            println!(
+                "       {}                  {}",
+                "yay -S arduino-cli".bright_cyan(),
+                "(Arch)".bright_black()
+            );
+        }
+        println!();
+        step += 1;
+    }
+
+    if !health.arduino_cli_ok {
+        // They need to open a new terminal after installing arduino-cli
+        println!(
+            "  {}. {}",
+            step,
+            "Close and reopen your terminal".bright_white().bold()
+        );
+        println!(
+            "     {}",
+            "(so the new PATH takes effect)".bright_black()
+        );
+        println!();
+        step += 1;
+    }
+
+    if !health.avr_core_ok {
+        println!(
+            "  {}. {}",
+            step,
+            "Install the AVR core and verify everything:"
+                .bright_white()
+                .bold()
+        );
+        println!("       {}", "anvil setup".bright_cyan());
+        println!();
+        // step += 1;
+    }
+
+    if !health.git_ok {
+        println!(
+            "  {}",
+            "Tip: git is optional but recommended for version control."
+                .bright_black()
+        );
+        if cfg!(target_os = "windows") {
+            println!(
+                "       {}",
+                "winget install Git.Git".bright_black()
+            );
+        } else if cfg!(target_os = "macos") {
+            println!(
+                "       {}",
+                "xcode-select --install".bright_black()
+            );
+        } else {
+            println!(
+                "       {}",
+                "sudo apt install git".bright_black()
+            );
+        }
+        println!();
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Platform-aware install hints (one-liners for the diagnostics table)
+// ---------------------------------------------------------------------------
+
+fn hint_avr_size_not_on_path() -> &'static str {
+    if cfg!(target_os = "windows") {
+        "installed but not on PATH (binary size reports will be skipped)"
+    } else {
+        "installed but not on PATH"
+    }
+}
+
+fn hint_cmake() -> &'static str {
+    if cfg!(target_os = "windows") {
+        "install: winget install Kitware.CMake  (or choco install cmake)"
+    } else if cfg!(target_os = "macos") {
+        "install: brew install cmake"
+    } else {
+        "install: sudo apt install cmake"
+    }
+}
+
+fn hint_cpp_compiler() -> &'static str {
+    if cfg!(target_os = "windows") {
+        "install: winget install Microsoft.VisualStudio.2022.BuildTools  (or MinGW g++)"
+    } else if cfg!(target_os = "macos") {
+        "install: xcode-select --install"
+    } else {
+        "install: sudo apt install g++"
+    }
+}
+
+fn hint_git() -> &'static str {
+    if cfg!(target_os = "windows") {
+        "install: winget install Git.Git  (or https://git-scm.com)"
+    } else if cfg!(target_os = "macos") {
+        "install: xcode-select --install  (or brew install git)"
+    } else {
+        "install: sudo apt install git"
+    }
+}
+
 fn check_dialout() -> bool {
     #[cfg(unix)]
     {
@@ -234,4 +413,4 @@ fn check_dialout() -> bool {
     {
         true // Not applicable on Windows
     }
-}
+}
\ No newline at end of file
diff --git a/src/commands/setup.rs b/src/commands/setup.rs
index 26cfd3b..1f07359 100644
--- a/src/commands/setup.rs
+++ b/src/commands/setup.rs
@@ -78,11 +78,22 @@ pub fn run_setup() -> Result<()> {
     if which::which("avr-size").is_ok() {
         println!("  {} avr-size (binary size reporting)", "ok".green());
     } else {
-        println!(
-            "  {} avr-size not found. Install for binary size details:",
-            "info".bright_black()
-        );
-        println!("       sudo apt install gcc-avr");
+        print_optional_hint("avr-size", hint_avr_size());
+    }
+
+    if which::which("cmake").is_ok() {
+        println!("  {} cmake (for host-side tests)", "ok".green());
+    } else {
+        print_optional_hint("cmake", hint_cmake());
+    }
+
+    if which::which("g++").is_ok()
+        || which::which("clang++").is_ok()
+        || cfg!(windows) && which::which("cl").is_ok()
+    {
+        println!("  {} C++ compiler", "ok".green());
+    } else {
+        print_optional_hint("C++ compiler", hint_cpp_compiler());
     }
 
     #[cfg(unix)]
@@ -137,6 +148,15 @@ pub fn run_setup() -> Result<()> {
     Ok(())
 }
 
+fn print_optional_hint(name: &str, hint: &str) {
+    println!(
+        "  {} {} not found. Install for full functionality:",
+        "info".bright_black(),
+        name
+    );
+    println!("       {}", hint);
+}
+
 fn print_install_instructions() {
     println!("{}", "Install arduino-cli:".bright_yellow().bold());
     println!();
@@ -161,3 +181,37 @@ fn print_install_instructions() {
     println!();
     println!("  Then re-run: anvil setup");
 }
+
+// ---------------------------------------------------------------------------
+// Platform-aware install hints
+// ---------------------------------------------------------------------------
+
+fn hint_avr_size() -> &'static str {
+    if cfg!(target_os = "windows") {
+        "bundled with arduino:avr core (avr-size.exe in Arduino15 packages)"
+    } else if cfg!(target_os = "macos") {
+        "brew install avr-gcc"
+    } else {
+        "sudo apt install gcc-avr"
+    }
+}
+
+fn hint_cmake() -> &'static str {
+    if cfg!(target_os = "windows") {
+        "winget install Kitware.CMake  (or choco install cmake)"
+    } else if cfg!(target_os = "macos") {
+        "brew install cmake"
+    } else {
+        "sudo apt install cmake"
+    }
+}
+
+fn hint_cpp_compiler() -> &'static str {
+    if cfg!(target_os = "windows") {
+        "winget install Microsoft.VisualStudio.2022.BuildTools  (or MinGW g++)"
+    } else if cfg!(target_os = "macos") {
+        "xcode-select --install"
+    } else {
+        "sudo apt install g++"
+    }
+}
\ No newline at end of file