XP Default Settings

Hi all, i recently used some software which now prevents me from using one
program, even after uninstalling both programs and reinstalling the effected
program on my PC.
I've tried repairing Windows XP by re-installing it, but no joy. I've also
tried "sysprep -nosidprep", but the majority of the setting stayed the same,
not resolving the original fault.


Is there anyway of resetting XP to It's original installation defaults.?

Thanks In advance for your help

Paul.