System Rebooting sudenly

[ofgarnica]

Help... I am having some problems with this PC sudenly rebooting, sometime I wil get a error message about a protection error message calling for me to press any key to continue then I get the stack overflow; so I go into the system.ini file and add MinSPs=4 and save changes; I even went up up in increments of 4 but no positive results. Ran a virus scan and found nothing. reinstalled windows 98SE and no changes. The motherboard is a Chaintech 7AJA, Athlon 1000 mhz AMD, 128mb Ram,30gb hhdd,ffdd,cdrom. Any sugestions will be appreciated.