I tell my clients the Windows registry is one of the truly bad ideas of the 20th century - but they're stuck with it because Microsoft likes the control it gives them.
These days when something goes wrong it's over half an hour to reload Windows, two hours or more to download and install the updates and patches (up to 80 of them now) and another two to four hours to reconfigure and reinstall their applications. That's pretty damned expensive.
I pull the machine into the shop whenever possible so I don't have to just sit their waiting for hours at full rate.