How to upgrade Windows 7 RC to RTM
Step 1: Just to be safe, you will probably want to back up your data (but you already knew that).
Step 2: Download the desired Windows 7 RTM ISO or have your upgrade disc handy. Make sure this is the same architecture as your current install as you cannot go from 32-bit to 64-bit, or vice-versa. You must upgrade to the same version.
Step 3: Mount the ISO using something like Daemon Tools, or extract it with your favorite ISO extracting tool (WinRAR, for example). Or, if you have the upgrade disc, make sure it’s in the drive.
Step 4: Open up the disc so you can see all the contents of it. In Computer, you will need to right click and select “Open” to avoid opening Autoplay instead.
Step 5: Copy all the contents of the disk (all files) to a new folder somewhere on your computer. I copied everything to a 4GB flash drive I have because I am upgrading multiple PCs.
Step 6: Open your new folder (or flash drive) with the contents you copied over from the Windows 7 install disc, and navigate to the Sources directory, and look for a file called cversion.ini.
Step 7: Open the file so you can edit it (I use WordPad). Make the following change:
Change it to:
Step 8: You’re done! You can run setup.exe directly from the folder without loading it on any media. Setup copies the files on to a temporary folder on your hard drive so it can complete the upgrade. Or if you have media or a USB drive, burn or copy the contents of the folder to the disc/media and run setup.exe directly from it.
Setup will now give you the option to upgrade your existing installation.