My processor is running at almost 1/3rd the speed it is meant to run on after installing a bios update.PLZ HLP

I have intel dual core processor and an hp pavillion m7382in pc. A month back I installed a bios update meant for my pc. Since then my computer slowed down. I have a dual boot os with vista and xp. I generaly work on xp so I thought that it must be normal but when I booted into vista the experience index showed the rating of my processor as 3.0 while earlier it was 4.7. Also the rating of my RAM went down from 4.6 to 3.9 despite the fact that my RAM is the same 1gb. Later I downloaded Intel processor id utility(from intel's website) which confirmed that my processor is running at a very low speed that is, 1.22GHz x2 while the expected frequency is 2.80 x2 GHz. I have already done a destructive system recovery from the recovery partition. This is not a virus problem as I have norton internet security 2008 which is fully updated and also there are no weird processes running in the background. PLZ HELP.