later versions as in vista/win7 are quite a bit more stable and in most cases it wont destroy your machine if you do something your not supposed to in the registry.
the reason is that ms decided to take a more unixy approach by also
saving all seettings in (you guessed it) an xml database.
the downside is size. i cant remember the folders name but its somewhere in system32. my win7 install takes at mint condition (fresh install) about 15 gigs ouch. well after installing the ms compiler and a few other things i ended up with it taking about 45 gig 20 gigs where
xml data, and believe me deleting "ANY" of that will break your pc

as for win7 you cant even delete it no matter what you do

that aside i agree a database can be a wonderfull tool for a lot of matters.
sqlite is one option another is gdbm if you dont like the sql syntax.