The only way to be sure that the system is clean (which should be the priority) is, IMO, to do a clean install.
The problem is that various files may have been damaged by either the infection itself or steps taken to remove infected files and there is no way (known by me) that a user can ascertain what damage has occurred and the extent of such damage.
You could try running sfc /scannow, which is a tool designed to replace missing/damaged system files.
LEARN how to use SFC.EXE (system file checker) in this article! - http://www.updatexp.com/scannow-sfc.html
You could also try doing a repair install, which will replace all the system files. Again, this is not necessarily guaranteed to be effective in certain situations...it's just one of the things a user can try.
How to perform a repair installation of Windows XP if Internet Explorer 7 is installed - http://support.microsoft.com/?kbid=917964
How to Perform a Windows XP Repair Install - http://www.michaelstevenstech.com/XPrepairinstall.htm
I don't use SR (I rely on systematic backup disk images), so someone else can give you some thoughts on that.