I've been quite annoyed lately. My PC (check specs in my sig) has taken to crashing every few hours of use, no matter what it is doing, although I've only experienced these reboots when I am using my PC for doing something (like playing games or doing homework) and as a matter of ironic fact, it has already rebooted once while writing this post. These frequent reboots are pretty much a daily occurrence, but if I am simply leaving my PC on to download a large file or just leaving it on to use later, it has never rebooted as far as I've known. They've been happening ever since I upgraded to a better graphics card, from an nVidia FX5500 256mb AGP card to my monstrous Gainward GeForce 7800GS 512mb Golden Sample AGP, it's quite a jump in performance. As a matter of fact, the reboots used to happen every time I played a game (any game requiring a fair bit of performance like Quake 4 or even Half-Life 2 at full GFX) for a maximum of about 10 minutes, and usually sooner with Q4. Eventually my PC wouldn't even boot up and packed in totally. I bought a new PSU in the hope that it would sort itself out. I bought a 400W unit, the same power output at my old one. My PC booted fine and worked without any rebooting or shutting down problems for a week, then I started experiencing them again. My instincts tell me I need to buy a PSU with a higher output value, possibly a 450W or 500W. The trouble is I have had this PSU now for about a month or so an I shelled out a lot of money for this damn thing, only to find these reboots are getting more and more frequent. I have plans soon to buy a PCI sound card as I only have an in-built one at the moment and I am having trouble with some games (like FEAR) where the sound doesn't play as it sound or no sound at all it heard. I fear (no pun intended) that if I do get a PCI sound card, that will need power which will cause my PSU to struggle even more and eventually collapse like my old one. I apologise for the lack of information about the situation, I hope I've given enough for someone to throw some advice my way or hopefully come up with some fix that will stop these reboots and say no to any possibility of the problem being something to do with power. As for software and programs, I have Norton Antivirus 2007, Windows Defender, HijackThis and ZoneAlarm Pro, and they all turn out no viruses, adware, malware, spyware or anything potentially harmful to my PC and I do checks with all programs at least twice weekly. So I don't think the problem is down to software in any way, but maybe I am wrong. Any information anyone can give is welcomed as I really am annoyed at the fact my high-end PC is cursed by these god-awful frequent restarts. Also, I wanted to ask but I am not sure, but if I did by say a 450W or 500W or more PSU, could it harm my PC by overloading it? I feel certain that the PSU doesn't try to offload all the power it can and that the PC only uses the power it needs, but I don't know for certain. Cheers in advance.