I have a machine running Win 7 beta build 7000 and while I admit that nuke-ing and re-installing win 7 would be the best option, I'd like to keep the install as is for now.
Is there any significant difference to the way you'd go about this in win 7 from XP as detailed In this article?
slight clarification: it will be a different board and different chipset
Vista and presumably 7 handles motherboard change much better than XP. You should be fine without any preparation at all - simply run it on the new system. My Vista installation survived a change from Core 2 Duo / i965 to an Athlon Dual Core / AMD690G and back without any problems.
If it is the exact same motherboard, you shouldn't have very many problems. Probably a lot of the hardware will redetect with their new IDs, but since all the drivers are already in place it will be fine.
If it is a different motherboard following the information in that link will probably be good. Though I recently changed motherboards and didn't worry about changing to generic drivers.
Keep in mind that nowadays if you significantly change the hardware windows will want you to re-validate.
In general you should be ok swapping the hardware out from under 7. One thing to beware, though, is if you're changing from non-AHCI environment to one that supports AHCI. (Advanced Host Controller Interface; used by SATA controllers to enable things like Native Command Queuing.)
If you enable AHCI (via a BIOS setting; it may be enabled by default, but unlikely) on the new board and you were not using AHCI before, it's likely 7 will fail to boot. Should that happen, consult this knowledgebase article. It'll get you up and running :)
(Alternatively, disable AHCI in the BIOS by switching your SATA controller to "legacy" or "IDE" mode.)