How to Undo a System Restore in Windows
If you have to do a System Restore, but it doesn’t quite go the way you wanted, you can undo system restore. In Windows, it is actually an easy process.
In Windows 7, you can undo a System Restore operation immediately after it’s done: Simply rerun System Restore and choose the Undo option that appears in the System Restore window. The System Restore is undone and your system is re-restored to the way it was before you ran System Restore.
Windows Vista? It apparently has no Undo command for System Restore.
To undo a System Restore in Windows XP, heed these steps:
Save your stuff!
The undo operation restarts your computer. Save now. Close open programs.
Start System Restore: From the Start button menu, choose All Programs→Accessories→System Tools→System Restore.
Choose the option Undo My Last Restoration.
Click the Next button.
Scary! Red! Text!
Click the Next button, which, honestly, should be relabeled the Undo button.
Windows undoes the System Restore operation. Your computer restarts. You log in.
Click the OK button in the System Restore window after the computer restarts.
You can then use the computer as it was before you shamefully attempted to use System Restore.
Obviously, the sooner you can undo after using System Restore, the better.