Has Microsoft, and its ecosystem, built planned obsolescence into PCs so as to force upgrades?

I know this is tinfoil hat territory, but hear me out. (The tinfoil hat on the left is being modeled by Elizabeth Kramer of Pleasantville, NY, daughter of the blogger Kathlyn Kramer.)

In theory the MTBF (Mean Time Before Failure) of all PC hardware extends not years but decades. There is no theoretical reason for an old machine to stop working, and refuse repair.

Yet that's just what is happening here.

It started a year ago. My 6 year old Windows 98 machine started acting up, refusing to boot, and Scandisk just wouldn't complete. A big part of the problem, I concluded, was the Norton security system I had installed.

But PCs were cheap so I changed it out. I got me a new Windows XP set-up for about half the price I'd paid for the original box back in 1998, and felt like I'd gotten off cheap.

Well, a few months later my wife's work computer started going through the same thing. Her bosses upgraded her, in time, to a laptop she could lug back-and-forth to work on the train, and I chipped in with a backpack to haul it in. She looks like a cross between Little Red Riding Hood and Quasimodo (except her cape is blue) but she's getting her exercise, she doesn't have to drive, and she can literally work anywhere.

Now, this weekend my daughter's Windows ME machine started giving me the same fits. I isolated the problem, again, to the security software -- McAfee this time. The system just won't load on start-up, and thus the machine won't boot for use. Worse, Scandisk wouldn't fully run until I took the security system off-line.

So am I crazy? Has this sort of thing happened to you or someone you love? Did you feel forced, by software, to upgrade your hardware (and buy a new Windows license at the same time)?

Just asking.