Illustrations
"Thunder is good. Thunder is impressive. But it is lightning that does all the work."
--Mark Twain
Locate Windows *.exe and *.dll files -- they do the work.
Locate the Registry hives -- they are not the registry.
Observe the Registry: (Listen to the thunder).
Do some work with Windows and compare the Registry before and after.
Change some options and see the changes using Registry Monitor from jv-16 Tools, or Ashampoo.
Install some programs: Power Calculator, Tweak UI, ClearType Tuner, SyncToy...
Start Regmon and watch the stream of access.
Alternatives to Registry entries:
Edit an *.ini file (Dropit)
Look at Firefox configuration.