In case it helps at all...
For reinstall or problem restore ops...
In cases where you have a working copy of Windows but the hardware has changed (i.e. m/b failure etc.), if you can get into Windows Safe Mode, then delete those devices (i.e. Device Mgr) with incorrect drivers, if you're lucky Windows will obligingly install the missing devices on start-up, saving from having to do a complete re-install. While I've gotten this to work with XP, my record is a win98 SE install that lasted >5 years, over 3 CPUs & 2 m/boards.
Since XP it's often easier to use the repair install, but that's not foolproof either. I've found it useful to not only export sections of the registry beforehand, but to have copies of the actual older registry files available. Regedit lets you import hives (for HKLM & HKUsers) & being able to look up & opt. export old keys has saved a LOT of time when getting everything working again.
Even if you opt for a re-install, a backup of your last good installation can work wonders. I work a lot with media, & have read dozens of complaints where after a re-install files won't open or play etc... Running MS's WinDif or similar compares files & versions between folders, like system32 for example, and can literally save days of troubleshooting.
In many situations, especially dealing with system files, I've found it very useful to store portions of disc contents as zip files. I'm not going to do a full disc restore of anything but the latest backup. For older backups it's usually difficult to look at let alone extract a few files from the often special formats -- assuming I even still have the backup prog installed, or that it will install on my current OS.
For critical apps, or when un-installing something I might want/need someday in the future, I'm almost religious about exporting and saving relevant keys in the registry. This has turned out to be a great habit with the arrival of Vista, since run compatibility is great, but install compatibility isn't.