How to upgrade Windows 7 RC to another version of Windows 7 without reformatting

If you, like me, installed the Windows 7 RC (release candidate) on your PC to give it a go and see what it was like & give it a test-tun, then you should, by now, have been made aware that as of the 1st of March 2010, 2-hourly reboots will occur. Your work will not be saved.

A few days ago (T minus 10 days and counting) from the 1st of March, I too received the same notification on my system. Of course, I knew it was going to happen – but I figure the 1st of March just crept up on me really quickly.

Anyway… if you’re like me and you HATE reformatting (and spending the next 3 days reinstalling everything and getting it back to the way it should be) with a passion, the good news is that you don’t have to reformat your computer to upgrade from Windows 7 RC to an RTM version of Windows 7. There are, however, some tricks you will need to perform.

Firstly, the Windows 7 RTM (release to manufacture) DVDs that you buy in shops etc are set to prevent upgrading from the RC to a RTM version like the one you would have just bought. When you insert the DVD and run it from within Windows 7 RC, you get a message (after you progress through a few screens and click the “Upgrade” option) that the RC version of Windows 7 cannot be upgraded.

Part 1 of 2:

The trick around this is to do the following…

1. Copy the entire contents of the Windows 7 DVD (ie: the official, proper, fully-finished version of Windows 7 that you buy in the shops) to your desktop in a folder.
2. When done, navigate to the ‘sources’ folder.
3. Open the file called ‘cversion.ini’ in an editor (eg: Notepad).
4. Change the second line from MinClient=7233.0 to MinClient=7000.0 …this tells the Windows 7 installer that it can upgrade from builds 7000 and above (most of you probably would have been running Windows 7 RC build number 7100).
5. Save and close the file.
6. Use Nero (or some other DVD burning application) to re-burn all of the files to a new DVD.

What we’ve essentially done in these 6 steps is edit one file on the DVD. Of course, most DVD’s are re-writable which is why we had to copy it to our computer first, change the file, and then re-burn everything back to another DVD disc.

Okay, so that should be enough to get you going… you should now be able to upgrade your Windows 7 RC (I think all of the RC editions were Ultimate, by the way) to the proper, finished RTM version of Windows 7 Ultimate. But there’s one small problem. What if you didn’t buy Windows 7 Ultimate. What if you just bought Home Premium, or Professional, for example? Then you will have a problem.

If the DVD you bought (ie: the DVD you used in Step 1 above) was anything but Windows 7 Ultimate, you’ll get an error saying that you can only upgrade the Windows 7 RC to a copy of Ultimate. You can’t go from Ultimate down to Pro, or Ultimate down to Home Premium… only Ultimate to Ultimate. But… there’s another workaround!

Part 2 of 2:

To get around this problem…

1. Open the Registry Editor (Start -> Run -> regedit)
2. Navigate to HKEY_LOCAL_MACHINE/Software/Microsoft/WindowsNT/Current Version
3. Change ‘EditionID’ to HOMEPREMIUM and ‘Product name’ to Windows7 HOME PREMIUM …or, if you want to upgrade from RC to PROFESSIONAL, then use the same steps as above but use the word PROFESSIONAL instead… and so on.

Now, you’ll be able to upgrade your Windows 7 Ultimate RC to a Windows 7 RTM version of Home Premium, Professional, Ultimate, etc! All my programs, settings, applications, files etc remained in tact. Even the stuff on my desktop was in the same position as where I left it! None of my applications needed re-activating either, but you will of course need to activate Windows within 30 days using the valid code provided to you when you bought it. But yay… it worked a treat!

PS: Microsoft recommends you do a clean format anyway, when going from RC to an RTM build. Always do a backup first. The above worked for me, it may not work for you. Don’t mess with the registry unless you know what you’re doing . Leave me a comment below if I’ve been able to help you or if you have anything to input. Thanks!

** Edit: 3/3/10 **

Since posting this article I’ve found that I only needed to setup two additional things on my PC… one was the Bluetooth connection to my mobile phone (took about 2 minutes to setup) and the second was Hamachi (the VPN software). The network connection that Hamachi creates was not retained after the ‘upgrade’, so I had to reinstall Hamachi – but it did remember my settings. Note that Hamachi will detect an existing copy of itself on your PC (which is true), but the ‘update’ function didn’t work for me, I just installed over the top and it found all my settings, re-did the Hamachi network adaptor and away she went!