For the three years I used XP, I desperately needed to use it's restore points to fix a serious problem. In both cases it failed miserably. I would pick a restore point, and XP would start to copy files like everything was OK, and then reboot. Just about the time the desktop started loading, I would get "restore failed", with no explanation. Researching the Internet showed it might
be my antivirus and/or firewall interfering. I turned both off and it still failed. Never did figure out why. Because of that, I bought DriveClone as an alternate, and it worked everytime I used it.
Fast forward to new Dell computer with Windows 7. Decided to try a Windows 7 restore point and I'm met with the error message attached. Nooo . . . not again. Disabled Zonealarm and Sunbelt VIPRE through msconfig, booted up and verified they weren't running. Tried the restore point again, and again it failed with the same message.
FINALLY, I tried accessing the restore point from Windows 7's "System Recovery" console (F8). Success! I've tried it a couple more times since with success, as long as I invoke it from F8 during boot up. Call me naive, but I didn't initially realize you could access that from F8. Seems odd to me that the error message doesn't tell you about this option.
Can I really really count on Windows 7's restore points to be more reliable then XP was? Yes, I do complete image backups on occasion, but don't always remember to do them often enough, and they might require going back farther in time then I would prefer.