This is not a problem, it's a feature. both addresses are yours. I like it since it helps avoid misdirected emails if someone accidentally adds a . in my address. http://mail.google.com/support/bin/answer.py?answer=10313#

I'm no expert on this kind of thing, but I have found/read that somehow this kind of software can regenerate itself via system restore. Disable XP
System Restore, (My Computer->Properties->System Restore), then run you're virus scanner/spyware detector etc again.

This has saved a couple of friend's PC's from being reformatted, so it's worth a try.

Peter