Probably mis-interpretation of the assembly code, some optimisations may not be correctly identified, like sse, or 3dnow specific instructions, this will case a stop error, followed by a reboot depending on what your pc is setup to do in such an event.
 
Often CPU overheating is a good candidate.
 
Followed closely by AGP bus errors, see the AMD patch about that, it is specific to athlon based systems.
 
Also the soundcard 3d extensions are good causes of errors
 
------------------
System Spec:
Athlon 800
Gigabyte GA-7IXE F4
128Mb SSi PC100
Radeon 64Mb DDR (10 out of 10)
Hauppauge Wintv Model 406
Realtek 8029 LAN (cnx to ISDN server)
Creative ES1371 (PCI64v)
Creative SBlive Value
Creative 48mx CDROM
Memorex TriMaxx200(DVD/CDR/CDRW, 6,4,24) Maxtor 91301U3 13Gb UDMA 4
LS120
 
If Jungle.com say it is not in stock it'll never be in stock, so don't order it.

WhenI saw the title of the post I thought...I bet this guy has a GeForce, and I was right. I was having similar trouble to what you describe, the strange restarts. I was running only win2k, so I don't know if it would have done it with win98. I thought it was a power issue since the Geforce is so hungry, but now I'm sure it was a problem with my cheesy MOBO, a Iwill Super7. I eventually got pissed off enough and bought a new Mobo and CPU, and that took care of it. What kind of Mobo do you have?
 
-=-=-=-=-=-=-=-=-=-
PIII 733 (fsb133) OC-->770
Asus P3B-F mobo
256 Meg Ram
Creative Soundblaster Live! Platinum
Creative FPS 2000
Creative Geforce2 GTS (32 meg)
13 gig Seagate HD
10 gig Seagate HD
ZipCD CDRW 2x2x24
Logitech Wireless Mouse and Keyboard

Thats a good one too, a 300W minimum Athlon approved PSU is recommended. Athlon mobo should be OK on the AGP power though? Maybe try disabling AGP 4x if you have it.
 
------------------
System Spec:
Athlon 800
Gigabyte GA-7IXE F4
128Mb SSi PC100
Radeon 64Mb DDR (10/10)
Hauppauge Wintv Model 406
Realtek 8029 LAN (cnx to ISDN server)
Creative ES1371 PCI64v
Creative SBlive Value
Creative 48mx CDROM
Memorex TriMaxx200(DVD/CDR/CDRW, 6,4,24)
Maxtor 91301U3 13Gb UDMA 4
LS120
 
If Jungle.com say it is not in stock it'll never be in stock, so don't order it.

I have a FIC SD11 mobo and I am using a 300W (approved amd) power supply. It also only supports 1x and 2x AGP (no 4x). I use powerstrip and have switched between both modes and have the same issue. I am leaning towards it being the soundcard but am still looking for advice. Thank all.

Could you try removing all your PCI cards (except the GeForce) and see if your system goes down. Then put them back in one by one. This process is no fun, but it might reveal your issue. I found that if I removed my Creative Live! card, that my comp would be more stable. That's when I knew I had to switch Mobos.
 
Hope this helps.
 
-=-=-=-=-=-=-=-=-=-
PIII 733 (fsb133) OC-->770
Asus P3B-F mobo
256 Meg Ram
Creative Soundblaster Live! Platinum
Creative FPS 2000
Creative Geforce2 GTS (32 meg)
13 gig Seagate HD
10 gig Seagate HD
ZipCD CDRW 2x2x24
Logitech Wireless Mouse and Keyboard

Status Update - I used spare components lying around and replaced the ones in my system one at a time to see if a card was the problem. I think it was the aureal soundcard that was causing the problem. I replaced with a semi-working old SBlive and so far no restarts. I will test this further but hopefully problem solved. The Aureal's A3D did not have any updated drivers (only beta - did not work) so maybe that was it. Thanks everyone for your input!

Excellent!