When Microsoft announced its cheap upgrade pricing for Windows 7 a while back, I advance purchased the Win 7 Professional upgrade edition (presumably to be released on October 22). In the meantime, I installed the RTM version of Windows 7 on my machine and it's working beautifully. I have not yet “activated” it, choosing to wait for the official product key in the upgrade version that I purchased (I can use the installed RTM version for up to 120 days without activation). Here’s my problem. I did a clean install with the RTM, not an in-place upgrade. I know from past experience that Microsoft product keys can be twitchy. Will I be able to use the forthcoming upgrade product key with a cleanly installed OS? I can't remember the circumstances, but in the past I've gotten messages stating that the product key I was attempting to use was not suitable for an upgrade install. I don't want that to happen again after fully configuring my machine and using it for a few months. TIA.