Use the Visual BASIC utility, xp_emergencyutil.exe, to make a special copy
of Regedit which is rendered immune to the malicious attack. Then you can
safely carry out the repair operation on that new copy. Please refer to: http://www.dougknox.com/
Click Windows XP Utilities (Lt. pane), then scroll down and click
Create Emergency Copies of Critical XP System Utilities
(Regedit, MSConfig and Task Manager)
Download the xp_emergencyutil.zip file and follow the prompts.
(Courtesy of MVP Doug Knox)