Just a small piece of info that some people may not know. You can use the Ultimate oem keys to do an anytime upgrade from home premium to ultimate. Example, a friend just did an anytime upgrade on a new acer laptop from 7 home premium to ultimate. He used one of the win7 acer ultimate keys. So I imagine that similar anytime upgrades can be done with any lower version of 7 to a higher version using the correct version oem key.
The same way you can upgrade from OEM Vista to OEM Windows 7 (but only the allowed upgrade ways as specified from MS). Afterwards just import cert (and key if you didn't type in during installation) and activate . But I think it's better to do a clean install.
'did that trick 3 times already, guess i had it reported earlier,none of these questions arose.. don't know if the OEM:SLP keys will be vendor specific though, as i didn't take the risk and upgraded with ultimate key from specific vendor you dont have to re-import certificate for anytime upgrade tried on toshiba , acer and dell just entered ultimate vendor OEM:SLP key in anytime-upgrade and it swallowed it whole and upgraded flawlessly
Old news to me I have been doing this sicen I bought my pc last year.... No risks no nothing, the only thing you should know its you need Slic 2.1 Cert and OEM:SLP key thats all folks......