If you buy something using links in our stories, we may earn a commission. This helps support our journalism. Learn more. Please also consider subscribing to WIRED

You know you’ve got a serious PC problem when your computer refuses to get through even the first phase of startup properly. If you can't get into Windows or macOS at all, then your troubleshooting options become a lot more limited.

Hopefully, you won't find yourself in such a scenario very often—or at all. But if you do have problems booting up your computer as normal, a recovery USB drive can save your system and restore access to your files and apps.

A recovery USB drive is a separate, portable flash drive that your computer can use instead of your main hard drive to start up from. Whatever issues you're having on your system can be bypassed, and you can get access to a variety of troubleshooting tools—or even reinstall the operating system, if needed.

These rescue drives are free to create and can be made in advance on your own computer (or using someone else's computer if yours is having issues). The steps are relatively straightforward, though copying the necessary software to the drive can take as long as a couple of hours, so plan accordingly.

When it comes to Windows, you can get started by searching for the Recovery Drive application in the search box on the taskbar: Click the program link when it appears to launch the setup tool, and check the Back up system files to the recovery drive box before clicking Next to get the most comprehensive backup.