PC always suddenly turn off by itself

[macosxtiger]

My PC always suddenly turn off by itself. Sometimes if I'm lucky enough I can use it for 1 hour, but most of the time, only 1/2 hour or less and then it will just turn off by itself in the middle of my work unpredictably. When I try to turn the computer on again, it usually turn on for less than 1 minute ( not even enough time to boot Windows or even go to bios menu ).

I've tried everything from changing the power supplies ( before I have 300 Watt but I've upgrade to 450 Watt ) but it does not seem to help. I have Athlon XP 2000  with Asus A7V266-C Motherboard. My Ide is all full ( both primary & secondary, master and slave ) with 1 CDRW, 1 DVD Rom and 2 Hard Drive. Memory is 512 Mb DDR SDRam.

Does anyone know what is the reason and how to solve this problem? Any help and suggestion would be greatly appreciated. Thank you very much.

[Computer_Commando]

Could be overtemp and the mobo is shutting itself off.  Monitor temps of CPU and hard drives.

[Flame]

Also, speaking of overheating.... Have your heatsink checked-out... You never know... I just had another computer user Instant Message me about a VERY similar issue, and it turns out that the heat sink was bad... Have a look at that... Also, have you checked for viruses?

[glb]Flame[/glb]

[Tom Burns Jr]

I'm having a similar problem, I let my PC sit overnight and it still does the same thing, I thought that it may be the hard drive, but I started it up without the hard drive in it, and it did the same thing. I can't get windows to boot up or anything. I was told that it may be the battery, so...off to Wal-Mart I will go, and if that isn't it, I will have the heatsink checked