Try going to Control Panel-> System -> Advanced System Settings-> Click on advance tab-> Performance Settings-> Adjust for best performance-> Apply and click ok.
If this help its probably using to much of your computers resources. Even though is has ok specs over time your gather alot of junk over time.
Have an older computer with Windows Xp?
The little sticker on the back with the Cd key will save you a hundred bucks.
If you do end up formating and installing Vista again you can Norton Ghost to create an image file of your HDD. Because there is always little things you will miss from your old HDD files.
Good luck
99 Problems but a CPU ain't one
if you havin computer problems
i feel bad for you son
I got 99 problems but a CPU ain't one
Hit me