This error seems scary, but all is not lost.

Sometimes Windows Update will go wrong in some way, rendering Windows unusable. It can also happen when a drive update goes wrong, or if you try and install more than one version of Windows on the same machine. This can often be fixed with a Startup Repair.

For that, you need your Windows CD or a Windows Recovery CD.

1. Put the Windows disc in the drive
2. Restart your PC
3. Enter your BIOS
4. Change the boot order to boot from CD/DVD first
5. Save and restart again
6. Choose your language, then click Next
7. Click Repair Your Computer
8. Choose your operating system (there will likely be only one listed), then click Next again
9. Select Use Recovery Tools That Can Help Fix Problems Starting Windows and click Next
10. Click Startup Repair

Your PC will restart again. Take the disc out and change the boot order in your BIOS back to starting from the hard drive first, if necessary. Windows should be working.

At this point, try Windows Update again and see if it wants to reinstall it. If the same problem happens again, try repeating the first eight steps above. After clicking Repair your Computer, choosing an operating system and clicking Next,

1. Click Open a Command Prompt
2. Type fixmbr and press Enter

(in Windows XP)

3. OR type BootRec.exe /fixmbr and press EnteR

(in Windows Vista or Windows 7)

Restart your PC and see if either of those fixes worked. If not, we’ve got a guide for repairing a broken Windows Update.

Note that if your operating system doesn’t show up, it’s likely that your hard drive has died. (That’s what happened in our case.) At that point, you’ll need to replace it. Good luck!