This has been a frustrating issue for a few months now. Using an AMD 3400 machine with XP pro. No problems for 2+ years. Then last spring all of a sudden the machine would not stay up more than a minute or 2 without spontaneously shutting down. The machine is located in an out building about 100 feet away from my router. I was using a cantenna to boost wireless reception. again it was working great until recently. i took the machine in to the shop that initially assembled it. they said it was the hard drive that was failing. i replaced that and the problem still exists. i tested the cantenna on another amd machine and no problem with that one at all ( i think that one was a 3800)
so something is happening with this wireless adaptor connection to the low loss cable that causes the machine to crash. the computer service people insist there is nothing wrong with the wireless card. when i check the card under control panel it does confirm that it is working properly

Check in the event viewer if there are any error related to the shutdowns.

Test also with another power supply, in case it is beginning to give up.

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