Macbook pro crash + artifacts

Hi,

I bought a late 2006 macbook pro from a freind which was broken as when it was loaded up the screen was distroted and had a checkerboard pattern on it. I re-installed osx + cleaned the dust+fans and this seemed to fix the problem but it still crashed + showed artifacts when it did.

After some use of the laptop it now infrequently crashes , sometimes displays horizontal lines ( but these can be removed by simply resizing a window) and crashing on waking up.

It has the X1600 gpu and with a fan control app temps(fans on increased speed) are about

cpu 45-65
gpu 45-60

during normal use

I am considering replacing the thermal paste to try and lower the temps ? Does anyone have any suggestions ? + I have attatched a picture of how it crashes

Thanks,
Rhys

 

Right, thank for the advice, still though i just dont understand why an osx re-install (mostly) fixed the problem , as it really was totally un-usable before ?