Computer turns off for no reason...wtf is going on?

[Muerto]

I recently re-built my parent's computer. I formatted it and installed Windows 98SE. All was going fine until it began randomly turning itself off. It never lasts more than 15 minutes before it shuts down. I've got all the most recent drivers for everything and the OS is up to date, and it's not over heating. This computer worked fine for me before I gave it to my parents and it's worked quite well for them too. It just started doing this. So what can make a computer randomly turn itself off?

Specs...

K6-3 400MHz
Epox EP-58 MVP3 mobo
128MB PC100 SDRAM
Voodoo3 2000
Maxtor 15GB 7200RPM ATA66 HDD
44X generic CD-ROM
SB AWE64 ISA
Realtek 10/100 PCI ethernet card
250W generic PSU
Windows 98SE

 

[OpalFrost98GT]

Sounds like the Power Supply is about to take a sh!t.

 

[Muerto]

Perhaps. I think I have an extra one lying around somewhere. I'll try swapping them.

 

[Villareal]

Since you reformatted and reinstalled Win98, check your power options properties to see if it's not set to shut down after 15 mins.

 

[mitso]

I had a similar problem. I found the female mboard power connector
terninals - which are 2 separate cylidrical halves - had split further apart.
After I pushed them closer together the problem was gone.
I guess slight thermal changes made some lose contact.