Now that I say this, it's gonna be the end of me, but my Windows 98SE partition has never been formatted in 3 years (this is through updates from 95-98-SE), even when I forgot that my peripherals may not work with my overclocked cpu. Doh! I play with shit, I use sound editing software, programming stuff, graphics programs. Oh, and I use IE5.

Major hardware upgrades I've done without having to reinstall:
New motherboard, CPU.
New ATA/66 PCI interface.
New Video Card (GeForce)
3rd Hard Drive

All at the same time.

It's just a matter of patience, and actually taking the time to uninstall software properly.