CPU temperature

I'm running a PIII 1.0ghz, asus mobo, 20gb hard drive, 384mb ram, nvidia geforce 2 TI 64mb agp video card, on win98SE. My computer has been locking up out of no where, both inside apps and at the desktop. It starts out happening at 1hour then on restart it happens at 30minutes then 15 then it wont restart at all. I removed my 3d card and put an old 2d card in, now it is working fine, the comp has been up for over 10 hours with no probs. Where is the problem here, is it the 3d card or?? Also I have Asus Probe and Hmonitor software running and both say the cpu temp is around 90deg, while the bios says the cpu temp is at 123.5 degrees. Which is correct? And can a 3d card overheat the cpu, if so should i replace the 3d card or what can be done?? thanks!

Yep v-card has a fan and its working, there is room for 1 or 2 more fans in the case.