...have a Biostar M7VKB mobo – socket A, 200FSB VIA KT133 chipset (not KT133a), which should, according to Biostar, handle anything up to an Athlon Thunderbird 1.4GHz 200FSB. I got a 1.3Ghz 200FSB and installed it (board is jumperless), put in the new fan etc.

When it powers up, everything starts up, but there's no video signal – after about 15secs, the whole thing powers off. I find I can't turn back on straight away – have to wait (for the PSU I feel), as I don't get that familiar crackle when I plug in the cord until it's ready to run again.

Not sure if it even POSTs, as it never gets that far. Was thinking it could be one of 3 things:

1. BIOS support – it can't handle the cpu in it's current revision, and needs to be flashed – even then, would there be settings in the CMOS for FSB etc?
2. heat – the chip powers down (can it?) after those 15s due to generated heat – shouldn't do this – I've applied the thermal paste, a copper shim & the heat sink (which is powered… have a 300W PSU – is that ok?)
3. knackered chip – it's dead – and the mobo powers down, as it "sees" no CPU. However, I did get a video output once to it, but it died soon after…
4. Biostar lie, and this board isn't compatible – I think I have rev 2.1 of the board, but this shouldn't matter as Chipset etc are identical.

I've flashed to a later BIOS, but it doesn't seem to make a difference...

Any ideas?

Make sure that your graphics card is in properly. What graphics card are you using any way?

with all the problems i had,,,,yours was simular to mine,,,,check your psu wattage,,bet u need more