Turns out it's not too hard to convince a Windows 7 disk image (from a real system) to boot in a VM, you just need to tell Windows not to BSoD when it fails to find your IDE or AHCI controller (basically the same as http://support.microsoft.com/kb/314082). Tweak some registry settings and then Windows will happily boot (a tiny bit slower) and start installing the required drivers for the rest of the hardware.
Only downside is it really pisses off Windows Genuine Advantage. ;)
Only downside is it really pisses off Windows Genuine Advantage. ;)