elitearmy :
Hi, i have problem with my games since i bought my gtx 780 ghz because many of my games are randomly crashing and freezing..is it because my psu or what?
It really depends on your PSU. Cheap power supplies may cost you quite a bit in the end (unscheduled upgrades/replacements as components die, and the PSU itself could die in a literal blaze of fire.) Cheap power supplies nearly always never deliver their rated power.
What brand and model of PSU do you have? Did you clean out your old graphics drivers and install the newest drivers that support your video card?