Virus problem! please help...!?

From few days i m facing one problem,oftenly MS DOS window pop ups automatically,whenever i close it appears again and again and above that window in a blue strip it is written svchost.exe,do anyone knows how to heal this virus.I found this file in windows folder but was not able to delete.I have win 2000-sp 4 installed in my system with AVG antivirus and adaware 2007 anti spyware.Can anybody tell me how to delete this virus and how does it comes