huuurgh, typing this from my re-motherboarded p2511
Found a 945-based btx form motherboard here, $19.99 (the overseas posting to the uk was $45 though )
Picked the old hunk of junk out, put the new one in, and discovered the d2660 was actually a reduced form btx board, about 2cm shorter along one edge. The intel 945 I've got fits in just about though. (intel on the left in the photo)
The old backplate didn't come off without a fight either
Everything managed to connect up apart from the front panel control. To cut a long story short i had to get some of these single pin connectors and connect up the front power on switch (it wont work without it). I've lost the 2 front leds, but poo to them. The main stalling point was that the red and neighbouring black wire in the bundle from the front panel aren't the two that connect to the two red marked pins (the on/off connection) on the new motherboard, but the blue and black wire... until that is done the computer will not switch on. That took some experimenting to find out, the more electronically-minded might have figured it out at the start but i'm strictly at the colour-coding level.
Once done, I did a repair installation on windows xp as all the "replacing your motherboard" guides say, and then i had to reactivate windows using the 25 digit key that happily was on a sticker on the computer casing,
At the moment I can't get the dvd drive to open (it has the fujitsu windows reinstallation disc in), but i'll see what I can do about that, it's not a biggy
And right now, 1 hour gone, and everything else seems to be ok (fingers crossed)