After reading through some of the posted questions regarding my problem, I just couldn't find the right answer so I am asking for some help.
I have a Dell XPS 400, Intel P4D, 2.8GHZ, that's about 4-5 yrs old. I just upgraded the PSU to 600W and added another 2GB RAM to total 3GB DDR2 RAM. The problem is, I also added a NVIDIA 9600GT 512GB graphics card and now the screen goes black after about 20min of gameplay. The CPU fans seem to speed way up and the whole rig vibrates and makes alot of noise. I have already taken off the CPU heatsink and blown it out and reapplied thermal compound, but it keeps shuting down. The games that shut it down are Crysis and Sims 3. I just don't know what to do at this point. Thanks much for any and all advice.