Hi Everyone, I'm having some real trouble trying to fix my parent's 3-4 year old computer. Two days ago it just froze when browsing the internet. I restarted and tried to run a virus scan (norton), 2 times, but after ~5min of scanning it freezes again. Now it's also freezing on startups randomly, during POST, when OS is loading, and at login screen. I also tried booting in safe mode and froze when it was loading. When it freezes, absolutely nothing works; the keyboard, mouse, everything just stops, sometimes the screen goes black, and once it even restarted on it's own. Thing I've tried so far: -Ran Check disk. -Norton and SuperAntiSpyware scans (neither fully completed) -Checked system logs, found no recent errors. -Boot from last known good config. -System restore (froze, didn't complete). -Opened the case and it was extremely dusty so i took a can of air and cleaned the best I could, also checked cables to make sure nothing was loose. After I opened the case and cleaned it out, it seemed to work for a while longer than usual, but it froze again after an hour or so into a virus scan. I'm leaning toward it being a hardware problem (maybe overheating?), but still not completely sure. I'm stuck here and any help will be extremely appreciated. Thank you! Edit: After installing the new heatsink it worked great. It's been used all weekend without a single problem now. Appreciate the help.