I can garantee you have a virus/trojan, i have seen this virus before and it resulted in a complete system re-install.
the virus that caused this for me was called:
in MRENDISS.sys and W22n51.sys
also a dll called AMVOO.dll
i forgot to add this happened on a few work computers, we found that the virus/trojan was spread using the autorun feature from USB sticks. also this virus sends out emails(lots of emails) we even had one guy who had his internet removed by his provider(sky) under the condition that he was unknowingly sending out spam.