When you try to install, update or start a program or a file, you receive the following error message: Error: Windows cannot access the specified device, path, or file. You may not have the appropriate permission to access the item.

When critical Windows system files are missing or corrupted, some Windows features may stop working correctly or Windows may stop responding altogether. If this happens, you can use the Deployment Image Servicing and Management tool (DISM) and the System File Checker tool (SFC) to scan your system files and restore any corrupted or missing files.

Corrupt registry keys on 64-bit operating systems. Corrupt registry keys that control the update data. Prevent new programs from being installed. Prevent existing programs from being completely uninstalled or updated. Block you from uninstalling a program through Add or Remove Programs (or Programs and Features) in Control Panel.

当关键的 Windows 系统文件丢失或损坏时，某些 Windows 功能可能会停止正常工作，或者 Windows 可能会完全停止响应。 如果发生这种情况，可以使用部署映像服务和管理工具 (DISM) 和系统文件检查器工具 (SFC) 扫描系统文件并还原任何损坏或丢失的文件。 DISM 提供修复损坏的文件所需的文件。 应在运行系统文件检查器之前运行 DISM。 为此： 打开提升的命令提示符。 在 “搜索 ”框中键入 cmd。 在搜索结果中，右键单击“ 命令提示符 ”，然后选择“ 以管理员身份运行 ”。 如果系统提示确认或管理员密码，请键入密码，或单击“ 允许 ”。 在 “命令提示符” 窗口中，键入以下命令，然后按 Enter。 完成命令操作可能需要几分钟时间。

When you start your computer successfully, the Windows Registry Checker tool (Scanreg.exe) creates a backup of system files and registry configuration information (including user account information, protocol bindings, software program settings, and user preferences) once daily.

When you install, uninstall, or update a program on a Windows-based computer, you may receive one of the following error messages. The Windows Installer Service could not be accessed. Windows Installer Service couldn't be started. Could not start the Windows Installer service on Local Computer. Error 5: Access is denied.

Get Help has troubleshooters you can run for many common scenarios. These often help resolve issues without the need to contact support. If a troubleshooter is available for your issue, select Run to start that troubleshooter.

Corrupt registry keys on 64-bit operating systems. Corrupt registry keys that control the update data. Prevent new programs from being installed. Prevent existing programs from being completely uninstalled or updated. Block you from uninstalling a program through Add or Remove Programs (or Programs and Features) in Control Panel.

You can start a scan for malware any time you like. Note: Microsoft Defender currently offers anti-malware on Windows, Android, and macOS. From the Microsoft Defender dashboard. If you want a deeper scan, instead of selecting Quick scan in step 3, select Scan options and choose the type of scan you want.

Get Help has troubleshooters for Microsoft 365 you can run for many common scenarios. These often help resolve issues without the need to contact support. If a troubleshooter is available for your issue, select Start to run that troubleshooter. Available Microsoft 365 troubleshooters.