Toshiba P105 Issues

I bought this laptop back in the summer of 2007. It was great, and ran like a charm, especially with games like FarCry and Flight Simulator. I was even able to play FSX for some time in medium settings wich was kinda neat since I was not expecting this laptop to run it at medium setting or even at all for that mater cause even though its got a 7900GT, I know for a fact you need something like a 8600 to run it nicely so I was impressed. Eitherway, recently, the laptop has been getting really slow in not only gaming but in video playback aswell.

In video games I play games that used to run smoothly and now they are a pain to play. Its like lag, but not really because the game runs smoothly for like 5 seconds and then lags a bit for like 2 seconds and it repeats. The game sometimes runs smoothly for an extended period of time but its really random.

When I play a video it lags really badly especially when I run a DVD. I know its the laptop and not Windows media player because it does the same with VLC. The sound keeps going though. When I run videos on my hard drive they sometimes run smoothly if I don't minimize the video but if I minimize it or start using photoshop (or any other program) in the bckground, it starts lagging almost 80% of the time.

I have recently installed Spybot search an destroy and am planning to do a complete virus check (I use AVAST home) and a defragmantation, and if that does not work I will have to reformat the laptop to factory standards.

But are these problems normal in the P105? are there any other things I can do to fix these issues?