Hi guys, ive had this PC for about 2-3 years and its been running fine till lets say 6months ago. It started randomly freezing and shutting down until one day it didn't want to boot at all. Then i went to some PC service and they said its graphics card prob and its dead. So i replaced old ATI radeon HD 3600 with VTX radeon HD 5450 . It was running fine for a few days. Maxing out CoD MW2 and Dota 2 then it started freezing and then it started to randomly shut down again. Now when it shuts down i have to reseat everything and after a few hours it boots fine. Prob is i play Dota 2 for eg. and it is good for sometimes 4 hours even then sometimes when i boot it, it shuts off when OS loads. Sometimes PC runs very slow and it freezes every few sec. and sometimes its ok(i cleaned registry and tried to free up RAM) If u can help me i would greatly appreciate it tnx! PC specs: AMD ATHLON 64 5000+ dual core 2.4 Ghz, 2GB ram, vtx radeon hd 5450, biostar mcp6p m2 mobo , 400W power supply, windows 7 ultimate