I had a similar problem which I think was caused by putting my Copper Gigabit network card in the first slot which shares resources with the on-board video. I moved the card to slot 3 and no more problems. Remember video intensive operations sharing IRQ's with another intensive operation such as over the Internet is not a good mix. Try not to use the slot sharing the video resources unless you run out. Then, put a low use card in like for USB printers, etc.
We started with a 400Watt power supply
3.2GB AMD Athlon XP Processor - standard heatsink
1GB RAM
120 GB WD 7200 HD
ATI All-in-Wonder 8500
Firewire PCI Card
SONY DVD
SONY DVD-RW
Standard Floppy
ASUS Motherboard
OS XP Pro sp1a
Bad Floppy replaced
Power supply upgraded to 450Watts
Heatsink upgraded
Memory replaced and tested
Currently the system is running under a load 43degrees C. No load 28 degrees C.
Voltage stable per ASUS probe
When attemmpting to run any processor intesive program after about ten minutes the system hard reboots. If the system is running under no load the system will run all night. Running intesive programs like EverQuest or SETI@HOME the system reboots. Running Word or a standard screen saver is not causing reboots. The heatsink was replaced to solve an earlier heat issues. The power supply was upgraded due to a thought that we might have a power issue.
ANY THOUGHTS I am tapped out. I have never had issues like this before and I have been doing this for seven years.
HELP??????????

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