ComputerWorld says that you can run a legitimate installation of Windows Vista for a year without activating it. Microsoft calls it a 'hack' the researcher that found the loophole calls it a 'feature.' Livingston, who publishes the Windows Secrets newsletter, said that a single change to Vista's registry lets users put off the operating system's product activation requirement an additional eight times beyond the three disclosed last month. With more research, said Livingston, it may even be possible to find a way to postpone activation indefinitely. Microsoft promptly labeled the registry change a "hack," a loaded word that is usually synonymous with "illegal."

"Recently it has been reported that an activation hack for Microsoft's Windows Vista operating system has been identified," said David Lazar, the director of the company's Genuine Windows program, in an e-mail. "Although these reports are purely speculative at the moment, we are actively monitoring attempts to steal Microsoft intellectual property."  "This is not a hack," Livingston shot back when Lazar's e-mail was read to him. "This is a documented feature of the operating system." To back up his view, Livingston pointed out links to online support documents where Microsoft spells out the pertinent registry key.

The following describes the Registry key that's involved.

Step 1. While running a copy of Windows Vista that hasn't yet been activated, click the Start button, type regedit into the Search box, then press Enter to launch the Registry Editor.

Step 2. Explore down to the following Registry key:

HKEY_LOCAL_MACHINE \ SOFTWARE \ Microsoft \ Windows NT \ CurrentVersion \ SL

Step 3. Right-click the Registry key named SkipRearm and click Edit. The default is a Dword (a double word or 4 bytes) with a hex value of 00000000. Change this value to any positive integer, such as 00000001, save the change, and close the Registry Editor.

Step 4. Start a command prompt with administrative rights. The fastest way to do this is to click the Start button, enter cmd in the Search box, then press Ctrl+Shift+Enter. If you're asked for a network username and password, provide the ones that log you into your domain. You may be asked to approve a User Account Control prompt and to provide an administrator password.

Step 5. Type one of the following two commands and press Enter:

slmgr -rearm
or
rundll32 slc.dll,SLReArmWindows

Either command uses Vista's built-in Software Licensing Manager (SLMGR) to push the activation deadline out to 30 days after the command is run. Changing SkipRearm from 0 to 1 allows SLMGR to do this an indefinite number of times. Running either command initializes the value of SkipRearm back to 0.

Step 6. Reboot the PC to make the postponement take effect. (After you log in, if you like, you can open a command prompt and run the command slmgr -xpr to see Vista's new expiration date and time. I explained the slmgr command and its parameters in my Feb. 15 article.)

Step 7. To extend the activation deadline of Vista indefinitely, repeat steps 1 through 6 as necessary.

Any crooked PC seller with even the slightest technical skill could easily install a command file that would carry out steps 1 through 6 automatically. The program could run slmgr -rearm three times, 30 days apart, to postpone Vista's activation deadline to 120 days. It could then run skip -rearm every 30 days, for a period of months if not years, by first resetting the SkipRearm key.

The program could be scheduled to check Vista's activation deadline during every reboot, and to remind the user to reboot once a month if a deadline was nearing. The buyer of such a PC would never even see an activation reminder, much less be required to go through the activation process.

If you happen to buy a Vista PC from a little-known seller, and the price was too good to be true, use Vista's search function to look for the string SkipRearm in files. You may discover that your "bargain" computer will mysteriously start demanding activation in a year or two — but your product key won't be valid.

I asked Microsoft why SkipRearm is included in Vista if it can be used to create machines that appear not to need activation for long periods. A Microsoft spokewoman replied, "I connected with my colleagues and learned, unfortunately, we do not have information to share at this time." (I can't identify the speaker because the policy of Waggener Edstrom, Microsoft's public-relations firm, prohibits the naming of p.r. spokespersons.)

In my testing of Microsoft's back-door loophole, I've found that the technique can be used to postpone the activation deadline one year or longer. It may or may not, however, work forever, as I describe below.

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In its TechNet documents, Microsoft recommends the repeated use of SkipRearm. How many times is "multiple times"? My testing revealed that the answer is, well, indefinite.

- On a copy of Vista Ultimate that Microsoft released in New York City on Jan. 29, I found that changing SkipRearm from 0 to 1 allowed the command slmgr -rearm to postpone Vista's activation deadline eight separate times. After that, changing the 0 to 1 had no effect, preventing slmgr -rearm from moving the deadline. The use of slmgr -rearm 3 times, plus using SkipRearm 8 times would eliminate Vista's activation nag screens for about one year (12 periods of 30 days).

- On a copy of the upgrade version of Vista Home Premium that I bought in a retail store on Jan. 30, slmgr -rearm also worked 3 times and SkipRearm worked 8 times before losing their effect. This combination would, as with Vista Ultimate, permit a one-year use of Vista without nag screens appearing.

- On a copy of the full version of Vista Home Premium that I bought in a retail store on Mar. 14, SkipRearm had no effect on extending the use of slmgr -rearm at all. This suggests that Microsoft has slipstreamed a new version into stores, eliminating the SkipRearm feature in Vista Home. That could mean that changing the key from 0 to 1 will now work only in the business editions of Vista - Business, Enterprise, and Ultimate - so corporations can use the loophole.

Where is the usage count of slmgr -rearm stored? Where is the usage count of SkipRearm stored? These bytes won't be hard for expert users to find. The use restrictions may be easily lifted. If so, this would allow crooked PC sellers to truly create machines that would never need activation, ever.