I won't waste time rehashing the argument over whether Windows Vista is any good. The fact remains that lots of people prefer Windows XP, and they'll go to great lengths to get it.

The problem: Windows XP "officially" went off the market on June 30, 2008, and computer vendors aren't supposed to sell new machines configured with any version of Windows except Vista.

Fortunately for XP enthusiasts and Vista vetoers, the PC marketplace still has a loophole or two in it. In response to pressure from customers, Microsoft has made some concessions for people who really want XP, offering a lifeline for users willing and able to wade through the company's convoluted downgrading program. The upshot is that virtually every copy of Vista Business or Vista Ultimate Edition is sold with a license for XP, which a computer manufacturer can exercise to install XP Professional on any Vista Business or Vista Ultimate PC.

But just because a manufacturer can install XP doesn't mean that it will. And just because its official policy permits it to sell XP machines doesn't mean that its employees understand that policy.

To find out how difficult it is to get a new XP machine these days, I asked the nine largest PC vendors in the United States--Dell, HP, Gateway, Toshiba, Acer, Fujitsu, Lenovo, Sony, and Asus--about the specifics of their downgrade policies. Then, to see how closely the official story synced up with the reality in the marketplace, I called sales representatives for each company and asked them whether I could purchase a new laptop equipped with XP from them.

The verdict? Downgrade policies are all over the map, and more than a few rank-and-file sales reps have a sketchy understanding of those policies. Some notebook PC sellers make getting XP preinstalled on a new laptop a snap; others don't offer it under any circumstance. As a rule of thumb, your odds of finding a machine with XP and a sales rep who knows how to configure a machine with that OS are far greater if you call the business sales line instead of the consumer sales line. (Be prepared to fib and say you're planning to buy 25 computers during the next 12 months.) Getting XP via online purchase can be tricky, too.

Here's how each manufacturer's formal policy--and informal reality--shakes out.