How did you use SR when the machine would not boot?
You could do this...
Turn on the computer, and press the 'f8' key to get to the XP boot menu.
Choose "Safe mode with command prompt". The system will ask you to choose the OS. It will say Windows XP Professional/home
At the command prompt, type the following EXACTLY as I have it written here:
The system restore console will appear. You will only have the choice to return to an early configuration. Perform the system restore to a time when all was well.
To turn off SR..
Right-click My Computer, and then click Properties.
Click the System Restore tab.
Select "Turn off System Restore" or "Turn off System Restore on all drives" check box.