Please see my subject line!
We got a Dell Inspiron E1710 laptop for my FIL(from the U.S and he is in India) with an express upgrade to Window vista home premium(bought it a month before vista was sold). It came with Media center XP installed and once the computer was upgraded to vista, the vista update assistant suggested deleting incompatible drivers and FIL has deleted it. So, the wireless mouse was not working but the computer was working just fine.
He didn't tell me all the details and when he asked me to fix the mouse, I immediately installed the driver software just to see what happened. Now, it takes me to activation of Windows vista and it asks me for the key and when I type in XP key or computer's product key, it doesn't activate it. Since it is an upgrade, I don't know what else to type in. The computer doesn't let me do anything at all other than taking me to microsoft's website to buy the key.Is there any way I can get to the device manager and delete the mouse driver? I can buy a new top of the line mouse instead of buying windows vista again. FIL is going to give me a hard time if I don't fix it. I am not extremely tech savvy when it comes to things like this. Please help me!

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic