Ready to 
Upgrade the Windows 7 RC to any retail version
Robert Hallock
October 6, 2009 2:04 PM ET in Tech
Updated 6 October, 2009: After investigation, we are the first to discover that it is possible to upgrade the Windows 7 release candidate to any retail (RTM) version of Windows 7. This procedure is now reflected in step 3
Windows 7 launches on October 22, and that means it will soon be time to jump ship on the release candidate. If you thought it would be as easy as popping in the retail disc and upgrading to the final version, think again: Microsoft put the kibosh on that idea by blocking upgrades from the RC. Luckily for you, there’s a workaround, and Icrontic will show you exactly how it’s done.
No upgrades for the Windows 7 RC? Lies and slander!
Fair warnings: Microsoft hit RC-to-Retail upgrades with the big, red denied stamp to avoid undesirable conflicts between files, settings and registry entries from differing versions of Windows 7. We think the risk is exaggerated, but this is the last stop for those who are squeamish about a clean OS. Ready to gamble? Read on!
Step 1
Insert the Windows 7 DVD in your PC and copy its contents to a folder on your hard drive. In the image below, we’re moving the DVD from Z: to some empty space we’ve created on our X: drive.
Step 2
Next, open the sources folder that was copied from the Windows 7 DVD. Locate and open a file named cversion.ini; it should appear as in the image below. Change the highlighted portion to read 7077.0, and then save the file.
This change tells the retail Windows 7 installer that any build of Windows 7 down to 7077 is eligible for upgrade, and that happens to include build 7100, better known as the Windows 7 release candidate.
Step 3
NOTE: If you are upgrading to the retail edition of Windows 7 Ultimate, this step should be skipped.
By default, it is not possible to “downgrade” the installed version of Windows 7 to a lesser edition. This is problematic, as the release candidate is the Ultimate version of Windows, while most users will be purchasing Home or Professional. Thankfully, this too can be overcome.
To start, crack open the registry on the release candidate box and navigate to the HKLM\Software\Microsoft\Windows NT\Current Version folder. In the right-hand pane, there are two registry entries named EditionID and ProductName, as can be seen in the following image.
Edit these registry entries to report the retail edition of Windows you intend to upgrade to. For example, users looking to upgrade the release candidate to the RTM of Home Premium would use HOMEPREMIUM for the EditionID, and Windows 7 HOMEPREMIUM for the ProductName.
Step 4
Now that you’ve slapped the involved parties into accepting one another, the last thing to do is to start the upgrade. Simply run setup.exe from the retail Windows 7 folder on your hard drive, and select upgrade when prompted.
Sit back, relax, and wait for it all to finish.
Final thoughts
Remember that Microsoft doesn’t officially support upgrades from the Windows 7 Release Candidate to the RTM. The firm has gently implied that, on rare occasion, it is possible for a system’s stability to be compromised as a result of an upgrade, so be sure to back up any important data before proceeding.
The entire process usually takes about an hour, but it could be much longer if you frequently use the My Documents or Program Files folders. When in doubt, let the installer run a little longer, and be sure to leave non-essential USB devices disconnected. When all is said and done, all you’ll need to do is activate to be on your merry.
It may be the retail edition Windows 7 Professional now, but an hour ago it was the Windows 7 Ultimate RC!
Questions, comments, concerns? Make sure to sound off in the comments below!
Note: It is not necessary to keep the files you copied from the Windows 7 DVD. You can delete them after the upgrade is completed.
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