Acer mailed two disks for their Windows 7 Upgrade kit, a clean copy of Windows 7 and a driver
/apps menu disk. The folder has what looks like a standard MS product key sticker labeled "Win Vista HmPrm - Win 7 HmPrm UPG Fulfill Acer Group."
One user with same Acer model decided not to upgrade from Vista so we attempted to clean install his copy on roommate's identical Acer model just purchased whose Upgrade Kit was only ordered yesterday.
The key was refused after installation. I strongly suspect this is because the Upgrade key is somehow coded to the Vista OEM key embedded on the intended machine's mobo. We will wait for the arrival of the key linked to this machine to activate.
The first user decided after seeing Windows 7 to go ahead with the Upgrade from Vista and the product key installed straightaway on the machine it was issued for, proving Upgrade keys are tied to the Vista OEM on these Acer machines.