Users of the Windows 7 beta have been to told to revert to Vista before upgrading to the forthcoming release candidate of the operating system. Microsoft has also confirmed that Windows XP users wishing to upgrade will have to buy a new version of Windows 7.

Microsoft, which admitted that going back to Vista will be "a pain" for users has said that it would block upgrades from the beta to the release candidate as, according to the company's Engineering Windows 7 blog, "upgrading from one pre-release build to another is not a scenario we want to focus on because it is not something real-world customers will experience."

The blog said that users would have to restore their PCs to Vista.  "We want to encourage you to revert to a Vista image and upgrade or to do a clean install, rather than upgrade the existing beta. As an extended member of the development team and a participant in the beta program that has helped us so much, we want to ask that you experience real-world setup and provide us real-world telemetry."

The problem with upgrading from one pre-release build to another, Microsoft said, is that the bugs or other problems users report in those scenarios are essentially worthless. "We don't always track them down and fix them because they take time away from bugs that would only manifest themselves during this one-time pre-release operation," the company admitted. Microsoft also acknowledged that it is demanding much from users by asking them to restore Vista before upgrading to the Windows 7 release candidate. "We know that means reinstalling, recustomizing [sic], reconfiguring, and so on. That is a real pain."

For people who refuse to revert to Vista, Microsoft offered a short list of instructions to circumvent the built-in check that bumps the user out of the release candidate installation if it encounters the beta. The process involves booting from that an external drive - such as a bootable flash drive - or another partition, and then modifying the "cversion.ini" file with a text editor.

Elsewhere in the blog entry, Microsoft reiterated that it will not offer an in-place upgrade to Windows 7 from the aging Windows XP. "We realized at the start of this project that the 'upgrade' from XP would not be an experience we think would yield the best results," the company said. "There are simply too many changes in how PCs have been configured; ...having all of that support carry forth to Windows 7 would not be nearly as high quality as a clean install."

Windows XP users will be able to purchase an upgrade edition of Windows 7 - those are always less expensive than the full version - but will have to wipe the hard drive, deleting all applications and data in the process, before installing the new operating system. However, Microsoft will provide a utility for moving files and settings that XP users can run prior to installing Windows 7.

Microsoft has not committed to a ship date for Windows 7's release candidate, but a leak last month proposed May for its public posting. Other sources, however, have speculated that Microsoft will issue the release candidate as early as this coming Friday.