Today I downloaded a torrent that included a DOCX file. After opening the DOCX in Open Office my computer froze when I closed the file. I keep a clean install, never run IE or Acrobat Reader and use Adblock Plus. I had never experienced a lockup before. Although I could move the mouse pointer, mouse clicks did nothing no matter where I clicked. The enter key also did nothing. Even after a hard reboot the system was totally locked. For the last couple of years I've used Revo Uninstaller along with ERUNT to revert to a previous state anytime I remove a test install of whatever. As many of you know ERUNT automatically backs up the entire registry daily on reboots. To repair my XP install I booted to Windows 7 on a different drive. Recovery entailed navigating to the ERDNT XP folder and running ERDNT.EXE after editing the INF file to change the drive letter reference. Reverting to the previous day's registry values unlocked the XP install. If you have yet to discover ERUNT I would advise checking it out. I keep System Restore disabled because it's an unreliable resource hog.
At least on Win 7, system restore does seem to work. I use it mostly to try apps., uninstall apps, and using system restore to delete all registries and traces. On XP, I found it to be more hit and miss.