I suggest you get CCleaner...
it's free... and has a registry cleaner built-in.
It will scan your registry-- and give you a list of unused software "pieces" ---among other things.
T
hese programs are not without some risk.
When you go to delete the excess keys, etc... it will ask if you want to save a backup (just in case)--
please do so-- then you will be able to restore it to it's present state in the
unlikely... but
possible event of a corruption.
It is a good program -- I use it regularly-- it is well-maintained by it's maker-- so it's right up to the minute all the time.
Download here:
CCleaner - Download
I use the "alternative link" personally.