I was unfortunate enough to receive a free copy of Antivirus XP 2008. 
It is really quite malicious and difficult to remove, it made rules in my firewall settings and was impervious to the standard XP 'Add/remove Programs' function. I unfortunately did not consult the Internet before I removed it, rather brutally, but I think it has gone. However it took out some of my desktop picture functions. The Properties tab is no longer available - gone, not just greyed out. It left me with a bright blue background (Blue Screen colour) and on start up it says that it is missing a file: C:\Documents and Settings\'my name'\Local Settings\Temp\.tt21.tmp.vbs.
So far everything else seems OK, but I would like to know if I can repair the O/S?