Hi pogopinchers,
Have you got a firewall running?
If not, somebody may be controlling your computer remotely.
If you only have Windows’ firewall (or worse, nothing) I’d recommend you install a good third party firewall like Zone Alarm Free and be very careful what connections you allow in and out.
http://www.zonelabs.com/store/content/support/zasc/gettingStarted.jsp?anchor=alerts&lid=zasupp_u
http://www.trendmicro.com/vinfo/secadvisories/default6.asp?VName=The+MEDBOT+Menace
http://www.trendmicro.com/vinfo/virusencyclo/default5.asp?VName=TROJ_HORST.GF&VSect=P
It may be worth running the specialist worm removal tool Stinger to look for Medbot:
http://vil.nai.com/vil/stinger/