Edited Regedit, can't re-open it + other issues

[FireFox2000000]

I followed this (http://www.thewindowsclub.com/change-default-program-files-directory-windows) guide, however instead of changing only the ProgramFilesDir to the E drive, I changed all the ones that had a C directory route under the Data side to an E. Now I can't open regedit again to change it back, it keeps saying it can't be found even though I'm clicking on the direct file in Windows Explorer, nor can I do installations of other programs and games.

"Windows cannot find 'CWindows\regedit.exe'. Make sure you've typed the name correctly, then try again."

So yeah, I have no idea how to change it back as my clicking on the System Restore link doesn't open anything. Task Manager doesn't open either. Windows boots perfectly fine though. And help would be appreciated.

[LogicalDrm]

Have you tried doing it on Safe Mode? You may need to use DVD etc to access system restore if registery has been damaged.