Under "mainstream support," you receive all the "critical updates" to keep the system secure, and additionally you may receive "optional updates" to improve or extend what your programs can do.

Under "extended support" you can ONLY receive updates and patches that Microsoft decides are "critical" for security and are sufficiently widely used by malware to be of concern to Microsoft.

When Win98 reached "end of life" Microsoft ceased "full support" and declared a date when "extended support" would end, but found that there were very large numbers of users who persisted in using it. The "extended support" (Critical patches ONLY) was continued for a rather long time after it officially expired, despite the fact that a very large majority of those still using Win98 were in countries where US export laws prohibited distribution (easily) of any subsequent versions, and where the majority of remaining users were using pirated/counterfeited copies. Reports are that there still are large numbers of Win98 users, virtually ALL using bootleg/counterfeit/illegal copies, but the status of support is unknown.

So far as has been reported, there are far fewer illegal users of WinXP, insufficient to force continued support in the same way they did for Win98, so significant extensions of the "extended support" period are unlikely. Any extensions beyond what has been announced would probably come only from "corporate users" with large numbers of WinXP installations still in use, and there's little information on how extensive those may still be.

If anyone still using WinXP can find a convenient way to upgrade to Win7 I would recommend doing so before it becomes impossible, as Win7 is "more secure" and better equipped to run 64-bit programs. There are some "inconveniences" in the change, but Win7 is arguably the best that's ever come out of Microsoft. The real problem is that it may force you to use "new versions" of some significant "productivity" programs that Microsoft has crippled to obscene levels (i.e. Office). Some "security setup" is a little different, but shouldn't present major problems for most users. The "quirks" mostly affect those on large local networks with lots of "user ident" problems.

Due to the inevitable "bit bloat" significantly more RAM and much bigger hard drives are advised for Win7, so new hardware is probably indicated if/when that switch is made. For Win7 a 64-bit processor also is very highly recommended.

It is impossible to say when WinXP will become "unusable," but it's unlikely to happen in a very short time if you want to be a little "stubborn" about keeping it up; but if you wait too long the only options for a "next system" may be quite horrid.

John