You could start with a search of the forums for revop, there are lots of threads relating to revop.
This is just one http://forum.avast.com/index.php?board=4;action=display;threadid=4669;start=msg33773#msg33773
You could try to follow it through and if you get in trouble, people will help. There is a wealth of information freely available on these forums.
You can do a google search for win32-revop, it returned 302 hits, this is just one of them, http://www.pestpatrol.com/PestInfo/t/trojan_win32_revop.asp
This should be enough to be getting on with.
Give a man a fish, feed for a meal - Teach a man to fish, feed him for life.
EDIT: For win2k
System Restore, a Windows XP feature, is similar to the [i]"Last Known Good Configuration" in Windows NT and Windows 2000. [/i] You can use System Restore to restore the computer to a previous state, using the backups that it makes of selected system files and program files. [i]Unlike the "Last Known Good Configuration" feature[/i], System Restore maintains multiple restore points. This gives you the choice of restoring your computer to any number of previously saved states.