How can I remove this annoying virus whatever called MBR:\\.\PHYSICALDRIVE0?

The computer in question runs under Windows XP. I did a random system scan with Avart and it detected that threat called MBR:\\.\PHYSICALDRIVE0. Avart delected all threats it found except that particular one. I chose several option on Avart: move to chest, delete, repair… but Avart did nothing, saying either the action was not implemented or object could not be found.

That virus has caused some troubles to my PC. Every time I insert my USB the computer does funny things and gives the USB a virus. And my browser seems to be slowing down too. Can any Fluther computer geek tell me how I can remove the virus?