Upgrading Windows 7 RC to RTM

If you’re like me, when you had Windows 7 beta on your system, you more or less expected to have to rebuild to move to the release candidate. With the release candidate, based on past history you fully expected to be able to upgrade from RC to RTM.

Surprisingly, that’s not the case. I don’t know the whys and wherefores of this decision, but I do know I don’t want to go through it. Fortunately, there’s a simple way to upgrade to Windows 7 RTM from RC, courtesy of Ron Schenone. Note that, strictly speaking, this scenario is not supported by Microsoft (though I highly doubt the question will ever come up). I’ll summarize the procedure here:

1. Mount your legal copy of Windows 7, either with the physical DVD or by using MagicDisc to mount the ISO.
2. Copy the contents to a writeable location (network file share, usb key / drive, etc.). I used a network file share that was available to all clients.
3. Browse to the \support folder.
4. Edit cversion.ini.
5. Modify the MinClient build number to a value lower than the build you’re running. If you’re running the RC, lower the number from 7100 to 7000.
6. Save the file.
7. Run setup from this modified copy, and the version check will be bypassed.

A few other notes from my upgrade experience:

• Log off all other users on the computer.
• Deauthorize any iTunes accounts for the computer. You can easily re-auth them when the upgrade is complete.
• I don’t know this last one for sure, but I believe the upgrade goes MUCH faster if you offload non-essential files from the system during the upgrade. When I upgraded my desktop computer that had a replicated file share with about 100 GB of data, the upgrade took forever. When on my second upgraded system I moved this kind of data off, it ran much faster. I do know that the Windows 7 and Windows 2008 R2 upgrades are actually a sort of wipe-and-load upgrade compared to the previous overwrite-in-place upgrade method, so it’s plausible.
• Use Treesize Free to compare (and clean up!) your disk space before and after the upgrade. You may find you’ve burned some space that can be reclaimed.
• You can also reclaim space after a successful upgrade by going into Disk Cleanup for the system drive (Right-click on the drive letter in Windows Explorer, Properties, the Disk Cleanup button by the pie chart). The list of of items that can be cleaned up will include “Files discarded by Windows upgrade”, but it will NOT be checked. In my case it saved about 1.4 GB of space.
• Before you copy all those files back (and you’re in the disk properties dialog anyway), go to the Tools property sheet and defrag your nice new upgraded system!

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