Three System Files To Backup Before You Reinstall Windows Windows installation CDs Your Registry  is one file you certainly want to backup before you  reinstall Windows , especially if you have licensed copies of software and you don’t know your license key. Most software stores its license key in the registry, so if you backup the registry, you’ll be able to reinstall your software.To backup your registry, click Start and search for regedit. Start regedit.exe, click the File menu, and chose Export. Special Drivers  are an essential backup if you use custom hardware on your computer. If you’ve paid dozens or hundreds of dollars for special hardware, don’t let the investment become worthless when you  reinstall Windows . Executables  including programs and special Dynamically-Linked Libraries (DLLs) are something else you may have gone to great effort to acquire which will be lost when you reinstall Windows. Go through the Add/Remove programs...