Can Windows 7 upgrade upgrade Windows 7 RC?

An XP disk or installation is supposed to validate an upgrade to W7 but it must be a clean install because an upgrade installation of W7 is not supported from XP. So if you have an XP disk, you should be OK.

However, it is very easy for people to get a discount on W7 without any prior OS or disks, simply by using the double install method to clean install with the $50 upgrade media and key. Time will tell, but that method is supposed to work.

In the "double install" method, one simply clean installs W7 w/o entering a key. Any W7 disk will alllow this kind of installation including the upgrade media which is the same as any other W7 media. (It's the key that differs.) So you've just installed W7 as an unactivated 30 day trial. Boot it up and from within that trial version of the OS, one simply inserts the upgrade DVD and installs W7 again, as an upgrade from the current trial installation, this time inserting the upgrade key when prompted. When that install is finished, W7 is full activated.

tannim said:

If I bought Windows 7 Upgrade for 49.99... could I use it to upgrade windows 7 RC instead of vista or XP assuming it even supports XP.

You would instead perform a clean install by the method outlined for a Vista upgrade disk since both Vista and 7 install very much the same way. Clean Install From Upgrade Vista - Vista Forums

It works! I know that from upgrading out 3.1 in years past to 95 with that being an upgrade disk while 3,1 was from 6 floppies. In those days you booted up from a floppy however and chose the "with cd rom support" option in order to startup the setup for 95 and later 98. Now you simply boot from the dvd itself.