First of all, could you list as much info as possible about the system:
CPU
RAM
etc..
And be more descriptive about the problem - i.e. do fans spin, is there any indication of any 'life' or what?
Did it work for a while and then die, or has it never worked (in his experience). Where did he get it from?
Also try unplugging as much stuff as possible - just leave CPU (& its heatsink of course), RAM, and a graphics card plugged in, and see if it will boot.
If still no joy there, try removing the motherboard from the case and resting it on a non-conductive surface (e.g. wooden table), and connecting just those few components again and see if you have any luck - if it works outside the case then you have a grounding issue, and should make sure that all the little standoffs inside the case match with holes in the mobo (so there's no 'rogue' ones to ground the mobo where they shouldn't)
It gets the signal when you plug it in.
Could you clarify that, by any chance? Do you mean it works if you unplug it, and then plug it back in, or do you just mean the power light changes what it's doing or something..
I used to have that mobo (IIRC) many years back, when I had my K6-2 350.
If you look at the board carefully, are there any capacitors (the little cylinders which kinda look like batteries) which look like they have a slightly domed top to them, or that appear to have 'leaked' at all? I've had a much more recent board than that die on me through failing caps. It might be possible to replace them, but they can be a pain to remove.
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A64 3200+ Winchester @ 250x10= ~2.5Ghz, ~1.41 Vcore
1Gb @ 209Mhz, 2T, 3-5-5-10
Voltmodded Sapphire 9800Pro @ 450/350 w/ modded VGA silencer 3.