Hi
If you use CCleaner's registry cleaner you should have a bunch of backup registries saved.
You could look at restoring the registry using the built in utility in CCleaner for restoring their backups, to a point before you made the changes in it.
If nothing else works it may be time to do a repair install, (at least in Windows 7 you can still do this, not so with W8).
This should get everything back up and working in a half hour or so.
It will keep all your installed software and data but replace all of the Windows OS files and take you back to default settings like a freshly installed copy of Windows.
http://www.sevenforums.com/tutorials/3413-repair-install.html
If you go this route print out the instructions and follow...