As I understand and I'll pass along the explanation. It's better to have the infected point available. Once cleaned then you eliminate and create anew.
Unfortunately, some anti-virus vendors recommend disabling System Restore before attempting malware removal so many folks still follow that advice. Turning System Restore off and then turning it back on has some risk associated with it since that feature does not always work as intended. Further, there is always a possibility of something going wrong during the malware removal process and you end up with more problems. Without a restore point to fall back on, you are then stuck with a limited means of restoring your system such as a Repair Install or Reformat. Although System Restore is not 100% guaranteed to work all the time, it at least gives you another option. When the system is clean, then the OP can create a new Restore Point and purge the old ones to prevent accidental re-infection.
See "System Restore and malware removal - what is best practice?
Also read Quietman7's reply today here (post #2)http://www.bleepingcomputer.com/forums/t/117374/what-happens-if-i-restore-and-have-a-virus/
Edited by boopme, 20 November 2007 - 11:43 AM.