Microsoft has never provided much in the way of "free support" for any OEM installed software. If it came on the computer, the computer builder is required to provide any support you get (and can do it for free or can charge for it).

A few months ago, Microsoft changed their "WinXP termination" policy to permit OEM builders to continue selling WinXP machines "until current stock is exhausted" but with a set date after which sales would be prohibited. The OEM has to sign a contract and pay in advance for the license for a certain number of copies.

Later, the rule was that all machines had to ship with Vista, but OEMs could offer a "downgrade" for free conversion back to WinXP (up to the number of WinXP licenses they had bought).

The "downgrade" permission has been extended, at last report to something like year 2014, so an OEM who has purchased a stock of WinXP licenses will be able to offer it until then. They will not be able to purchase new licenses, so when they run out, they're done.

You can check out the details at the Microsoft Life Cycle page. (It has changed fairly frequently in recent months.)

You are, and will be, required to "authenticate" your Windows installation in order to get Critical Updates, regardless of whether your version is current or obsolete. Critical updates are still occasionally offered for Win98SE, although they come out fairly sparsely.

Win2K remains in fairly widespread use, but suffers from one "defect" that makes it something of a risk for Internet use, in that it requires an open and visible external port that can make it easily found by malware distributors. All later versions can be "fully cloaked." (There are still open(able) ports, but they're not as easily visible to intruders.) If you're using Win2K, it might be worthwhile to consider a full "Internet Suite" style of anti-malware rather than just a simple AntiVirus, although "good operating practices" and self-restraint (with at least excellent AV) are still the main things needed to avoid currently common infections.

John