Compaq V5000

Hello, I was wondering if anyone could please help me, I am trying to provide as much information as i can. So, I had my computer recently fixed for viruses. I get the computer running again and made a huge mistake of trying to use a USB drive i have which then starts randomly popping up messages and changed my desktop bg to ATTENTION YOUR COMPUTER HAS BEEN INFECTED WITH SPYWARE. So Immediately i try running Malwarebytes..which does not work, nothing would. It would not let me click on anything. I remember taking a computer class b4 which i learned that sumtimes USB's can become infected so im guessing thats what has happened. =( So after restarting it few times thinking maybe i could atleast click something afterward, it would not start at all....well it would start. I got the Compaq title screen and at the bottom right b4 it starts up theres a white loading bar that fills as the computer loads....to sign on and ....its not doing anything it gets two bars and nothing works and its as if the fan or sumthing is not running as hard as it does when it starts up ...it starts off strong but then gets very soft, likes its not getting enough pick up. I am hoping that its just the viruses and that there is someway i can get around to opening up and if any of you may know a solution to getting it started I would greatly appreciate it..O n btw. Yes, i have tried logging in to safemode....you name it...just when it gets to the actual startup it freezes...screen goes completely black. The computer is the Compaq Presario V5000 and runs on Windows XP media edition 2005 i believe. Again thanks guys. =) I really would appreciate any knowledge u may have on it.