Update:
Turns out the HD I was using was failing.
New resutls:
You can run an upgrade using an OEM vista home premium disc from XP home sp2.
Notes:
Selling the OS in this manner is a violation of the OEM ToS.
Using this method to reinstall Vista on a system with a valid retail or upgrade license for vista should be OK.
OEM DVDs only contain 32 or 64 bit files. I believe retail copies contain both.