I don't think it will work since you wouldn't have the sticker with the product key. In the upgrade it will ask for the product key and for OEM products you need that sticker. Unless you can find some OEM stickers which people didn't want then you can use that to upgrade.
I used daz loader when I upgraded my laptop to SSD and couldn't figure out how to move the recovery partition. So, if I call HP for new recovery media, get a valid OEM serial, but then want to reformat in 6 months, my $40 upgrade will be worthless? Or do I have to reinstall windows 7 with the genuine key first?
"I'll bump this because I didn't see anything about this in the FAQ and have been wondering also. " Dude, you wanna see FAQ with Daz loader in particular, not happening dude! Gotta wait few more days, and we ll try it out!
According to Brandon LeBlanc the upgrade advisor will even work on pre-release versions of Windows 8.
I'm wondering if you would be able to use the retail upgrade and activate it legitly if you have window 7 ultamate activated using a mod bios slc 2.1 ? Would the same key I used to activate win 7 work to install Win 8. $39 or even $69 isn't bad price but if I can't upgrade what I have then it's a total waste of $'s?