Oops!! Seems like I got confused between boot sector virus, and BIOS virus. Thanks to freedog's post, I got reminded of it.
Boot sector virus can be removed by using an antivirus rescue CD... BIOS virus cannot be removed by that. As freedog says, BIOS virus can only be removed by flashing of the BIOS... and that can be a risky task.
Here is an article I found for BIOS virus :
http://www.ehow.com/how-does_4809843...ios-virus.html
As the article says, BIOS virus are very rare.
Boot sector virus may or may not get removed by formatting. For that, wiping the disk can be necessary. Also, as I said earlier, you can use an antivirus rescue CD.