Enhance 7-zip detection on Windows

- Try 7z from PATH first
- Fallback to default installation directories:
  - C:\Program Files\7-Zip\7z.exe
  - C:\Program Files (x86)\7-Zip\7z.exe
- Better error handling for extraction failures
- Improves compatibility with standard 7-zip installations on Windows

usb_creator_gui.py

@@ -105,10 +105,36 @@ class WorkerThread(QThread):
 
     def extract_iso_windows(self, iso_file, extract_dir):
         # Use 7-zip to extract ISO on Windows
+        # Try 7z from PATH first
+        seven_zip_cmd = '7z'
+        
         try:
-            subprocess.run(['7z', 'x', f'-o{extract_dir}', iso_file], check=True)
+            subprocess.run([seven_zip_cmd, 'x', f'-o{extract_dir}', iso_file], check=True)
+            return
         except FileNotFoundError:
-            raise Exception("7-zip not found. Please install 7-zip for Windows.")
+            # Try default 7-zip installation directory
+            default_7z_path = r"C:\Program Files\7-Zip\7z.exe"
+            if os.path.exists(default_7z_path):
+                seven_zip_cmd = default_7z_path
+                try:
+                    subprocess.run([seven_zip_cmd, 'x', f'-o{extract_dir}', iso_file], check=True)
+                    return
+                except subprocess.CalledProcessError:
+                    raise Exception("7-zip extraction failed.")
+            
+            # Also try Program Files (x86) for 32-bit systems
+            default_7z_path_x86 = r"C:\Program Files (x86)\7-Zip\7z.exe"
+            if os.path.exists(default_7z_path_x86):
+                seven_zip_cmd = default_7z_path_x86
+                try:
+                    subprocess.run([seven_zip_cmd, 'x', f'-o{extract_dir}', iso_file], check=True)
+                    return
+                except subprocess.CalledProcessError:
+                    raise Exception("7-zip extraction failed.")
+            
+            raise Exception("7-zip not found. Please install 7-zip for Windows or add it to PATH.")
+        except subprocess.CalledProcessError:
+            raise Exception("7-zip extraction failed.")
 
     def modify_root_password(self, iso_dir):
         # Find and modify preseed file