[derefr]

My guess is that it's the keeping around of third-party drivers made for the previous OS that causes the majority of upgrade "rot."

If older editions of Windows just forcibly purged all the drivers when you upgraded, and told you to reinstall them afresh from the installation CD/OEM site (where you'd then get a version that's maybe for your current OS instead), that could have saved everyone quite a few headaches.

Then again, with major peripherals (displays, keyboards/mice, Ethernet cards, USB controllers) being much less standard than today, ripping out the OEM's driver could wedge your computer.

[eric_h]

Certainly. I honestly never even expected a Windows update to be guaranteed to succeed simply because the surface area for them to test is unimaginably large - the same was not true for Macs (at least once OS X got good), so when a Mac OS upgrade failed I was generally more surprised.