You can go here:
http://www.spywareinfo.com/~merijn/downloads.html
to get an auto-removal tool for this infection. I don't think the tool is up to 121 yet, though. What I always do to remove these things manually is boot from the XP CD (or boot disk for previous versions) and hit 'r' at the first screen where it's waiting for you to do something. Then you can navigate to the file and rename it. Please note that some of the msg*.* files do belong to Windows, but anything in the 100 range is bad (is, 115, 116, 120, etc.) To remove all this stuff I usually run Spybot Search and Destroy, Adaware, CWShredder and Kill2Me. Then check all Hosts files on the computer (I use HostsFileReader for that) and finally run HijackThis. Most or all these tools can be found on the page I listed or on:
http://www.spywareinfo.com/
in the downloads section. HijackThis should ONLY be used by or with the help of an expert. It lists EVERYTHING, good and bad. There are also some excellent forums on Spywareinfo.com and the people there are very helpful, so long as you don't ask them to explain themselves and just accept their word as offered. That shouldn't be a problem. They reall know what they're doing.