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When the power shut-off it probably corrupted the system restore and that would make it very un-usable.
Restore tool at a command prompt in Windows XP
Troubleshooting missing restore points:
How to Use System Restore – Bert Kinney MVP
Davory: Data Recovery as easy as it gets
In this case, I recommend trying to reinstall System Restore, here's how:
You will need to be able to view hidden files, so go to Start>> Control Panel>> Folder Options>> View tab.
Under Advanced settings, place a check mark in: "Show hidden files and folders".
Then uncheck: "Hide extensions for known file types".
Click Apply, then OK to exit.
Open Windows Explorer, then go to Windows>> inf folder.
Open the inf folder and find a file named:
Right click this file and select "Install" from the resulting menu.
Note: This procedure will delete all restore points from your old installation and recreate a fresh installation of System Restore.
When finished with this reboot the system and try going back into system restore and see if it works.