Microsoft has begun reminding millions of testers of Windows Vista's beta and release candidate (RC) previews that their trial runs end on June 1.

Cori Hartje, director of Microsoft's antipiracy efforts, became the first company executive to note the impending deadline. "As a reminder to those that helped with Windows Vista beta testing, the beta installations are set to expire at the end of May 2007," said Hartje in a Q&A that Microsoft posted March 30 on its public relations Web site. "So customers need to decide if they want to move to Windows Vista or back to Windows XP if they have test versions of Windows Vista on their PCs."

Details on how best to do that, however, are scant. Despite repeated requests to clarify the exact procedure beta and RC users need to take -- and whether Microsoft will provide either guidance or offer a discount to testers -- the company declined to spell out its plans.

What information the company has published is on last year's Customer Preview Program (CPP) site, which points to the June 1 expiration date and explains that once installed, the Vista previews don't allow for operating system rollbacks. "You cannot roll back to the previous operating system installation -- you will either have to acquire and install the final released edition of Windows Vista or reinstall a previous edition of Windows," the site reads.

Some hints, however, can be found on Microsoft's Vista support forums:

-- Only a full version of Vista does the upgrade from Beta/RC to final. Multiple threads on the Vista forums note that it's not possible to do an in-place upgrade from Vista Beta or RC using a final, retail upgrade version of the operating system.

"You can't use an Upgrade edition to move from Beta/RC to final. Has to be a Full version," said a user identified as Richard Harper. That means Beta/RC users can't take advantage of the lower-priced upgrade Vista stock-keeping units (SKU) to retain their Vista settings and installed applications when migrating to the real deal. The price difference on Vista Ultimate is dramatic: $259/£204 list for the upgrade edition, $399/£310 for the full version. And that's important because ...

-- $399 buys you in-place upgrade. If testers wondered why Microsoft gave them the most powerful, and expensive, Vista last year, this may be a clue: To do an in-place upgrade from a Vista preview to the final code requires not only a full edition, but a full edition of Ultimate.

"Just as in all past [Microsoft operating systems], downgrading isn't supported," said Dave B. Another user, Chad Harris, was more specific. "It has to be a Full version of Ultimate ... any other version (Home Premium, Business) is considered a downgrade to Ultimate and is not allowable."

-- Revert to resume. To take advantage of lower-priced upgrade editions of Vista, or to move from the Beta/RC Ultimate SKU to a less-featured version, like Home Premium, testers must reinstall an earlier operating system -- likely Windows XP -- before upgrading from that to Vista final.

"So if I return my laptop to XP, then if I bought the upgrade version of Vista, it should work right?" asked NoSpinVette. Rick Rogers answered with a simple "Yes indeed." The reinstallation of XP, of course, deletes all data on the boot hard drive and so requires testers to backup data files and reinstall applications on the Vista-powered PC after the upgrade is completed.

Those hassles didn't sit well with some dedicated beta testers. "Do you mean to say that because I installed Vista RC2 over XP, I screwed myself out of upgrade pricing? If so, seems like MS is punishing beta testers," said a user labeled as "tom."

Others, however, brooked no whining. "You should've known better than to install a beta over your primary operating system/primary computer. Microsoft warned users not to do that," responded another poster identified as Michael.

The migration issue isn't trivial, if only because of the numbers involved. At one point in 2006, Microsoft boasted that 1.5 million users had downloaded Vista RC1 and said it expected an additional 1.5 million to download RC2.