I have to came to know that one of my brother PC was attacked due to trojans and viruses .It was always restarting saying RPC service launched however i searched all over the net but still i am facing the problem and in the final i downloaded and adaware and removed some viruses.This has helped me to stop RPC problems

you can get further nfowmations on microsoft

MS03-026: Buffer Overrun in RPC May Allow Code Execution
http://support.microsoft.com/default.aspx?scid=kb;en-us;823980