I've written in the past that Microsoft will support upgrading from the Beta version of Windows 7 to the upcoming release candidate (RC) version. And it's true. But as Microsoft reveals in a typically long-winded Engineering Windows 7 blog post, it's going to take a bit of work.

These instructions will be brief.

LOL. That sentence appears a whopping 1,058 words into the post, by the way.

Anyway...

Here’s what you can do to bypass the check for pre-release upgrade IF YOU REALLY REALLY NEED TO:

  1. Download the ISO as you did previously and burn the ISO to a DVD.
  2. Copy the whole image to a storage location you wish to run the upgrade from (a bootable flash drive or a directory on any partition on the machine running the pre-release build).
  3. Browse to the sources directory.
  4. Open the file cversion.ini in a text editor like Notepad.
  5. Modify the MinClient build number to a value lower than the down-level build. For example, change 7100 to 7000.
  6. Save the file in place with the same name.
  7. Run setup like you would normally from this modified copy of the image and the version check will be bypassed.

These same steps will be required as we transition from the RC milestone to the RTM milestone.

So let's be clear here: Upgrading build over build is never recommended. If you can do it, do a clean install of the RC instead.

Oh, and as for RC-to-RTM or Beta-to-RTM upgrades, I'd been told previously that this would not be supported. But the workaround above will apparently work. Seriously, do not do this.