You would need to buy the Full version of Windows 7
Upgrade from Windows 7 RC (beta) to Final
Sorry, you can't upgrade from the Windows 7 RC to the retail version. You have to have XP or Vista installed first, then move to Windows 7 with an upgrade disk. Or buy the full version and do a clean install on your computer.
The rules according to Microsoft:
In order to install the upgrade version of Windows 7, you must have a qualifying Windows operating system installed and activated. You cannot install an upgrade version of Windows 7 on a blank hard drive. The installation procedure does not ask you to insert
a Windows disc in the drive for verification, the actual qualifying operating system must be installed.
If you do not have a qualifying Windows operating system installed with a genuine license activated , then you cannot use the upgrade version of Windows 7 - you would need a "full version" Windows 7 license.
1. A qualifying Windows operating system must be installed.
2. The qualifying Windows operating system must have a genuine license (product key) and it must be activated.
3. To upgrade, boot to the qualifying Windows desktop, insert the Windows 7 Upgrade disc in the DVD drive.
Please note: All users of the Windows 7 Release Candidate (including Windows Vista users who have upgraded to the Release Candidate) must do a clean installation of Windows 7 RTM. Please keep this is mind as you consider downloading the Release Candidate as
opposed to waiting for the general availability release.
Thanks again for your help in reaching this important milestone. We hope that you will join us in testing the RC and finishing Windows 7!