This is a useful guide you may want to take a look at :-
http://realsecurity.web.officelive.c...vemalware.aspx
(Written by one of the members here).
You may or may not need to carry out all the steps suggested but it's a good reference point. Read it through first before you attempt to clean your PC. If you feel daunted by the task you could also seek help from one of the help forums he lists under "further help".
Good luck with it.