Switching MOBOs quick question

Is there a faster way than switching out mobos then doing an over the top install for M$ 2000 Pro?

The thing is I have an Epox8krai which my XP2600 is running on and an Abit Nf7 which my XP1700 is running on now the Epox doesn't have heatsink boltholes for mounting of a sink like the SLK947 which I want on the 2600.

So whats the best way to do this HDDs in both system have already been loaded with the OS but I'm not about to change the HDDs around cause one is a 20 < folding rig and the other has 2 60s in it.

Thanks for all your time in this matter,
Ambient Fiction

If you're lucky, you won't. But it's recommended anyway.

Yeah well as we all know I'm not lucky I'll have to reinstall both OSs