pc Boot fails 50% of the time

When I boot my pc, it fails (shuts down) about 50% of the time, JUST BEFORE posting (if I here a beep, it will boot just fine)
Note that when it gets past the beep thingy, it does not crash of shut down. Never had i power failer or crash once the machine is up

I have a Intel P4 2400 on a Abit KT7 motherboard, using 1 SATA HD, one UDMA133 HD, a DVD writer and a CD writer. Also use SB soundcard, have netword card and Geforce4 Ti video card. Power suply is at 350Watt i think, but already tried replacing that, didn't solve it.

Any help would be welcome, caus I have no idea how to fix this problem

 

Do you see anything on the screen when it does not boot?

The beeping occurs when the machine will boot? Or you hear beeping if the machine is not going to boot? How many beeps?

Since you seem to have many devices attached, basic troubleshooting would be to try and startup with a bare bones system, and start plugging in devices one at a time to see if one of those devices will prevent the system from booting. This includes PCI cards, IDE, SATA (not including boot drive), etc.

 

The beep announces succesfull post. You know, when you boot your computer, it gives a little beep, then the screen goes on and the machines starts booting. If it fails, it fails just before the beep
the strange thing is that all hardware seems to work perfectly when the boot succeeds... even if stressed

 

Try unplugging all the devices in your computer except for CPU, memory, video card, and the HDD with the OS on it. Try to boot up 4 or 5 times.

If it boots up normally, then start plugging devices in 1 at a time and boot it up a few times. I suspect it may be your soundblaster card. Quite a few people have had problems with compatibility with SB cards and especially the Audigy line.