Messed up the Registry! No Program can start, not even regedit

Hi,
today i wanted to change the default program files direction to "Q:\Program Files\" instead of "C:\Program Files". So what i did was:
-I opened regedit
-HKEY_LOCAL_MACHINE\Software\Microsoft\Windows\CurrentVersion\
-and i just changed "C:" in every value that contains it, to "Q:"

Now, after i rebooted my pc for the first time since that, i cant open any programs with their executables located on "C:". Neither can i move anything to or from "C:". Not even Windows programs like "regedit" work.
It keeps saying "C:\Program Files\Teamspeak 3 Client\teamspeak.exe" cannot be found! Please make sure if you spelled it right!" (Sorry if the translation sucks, i'm german ^^).

And i also got an error like "class not found" or something.. please help me!

Just as Windows begins to boot, press F8 for Advanced Boot Options. Try Last Good Configuration. Next try Restore System to previous point in time.

paul1149 said:

Just as Windows begins to boot, press F8 for Advanced Boot Options. Try Last Good Configuration. Next try Restore System to previous point in time.

Thats exactly the problem.. I cant even do that.. when i try to open it, it says "System Recovery could not be started". I need to somehow put it back to default.. still i have no idea how

Last Good Config also didn't work?

paul1149 said:

Last Good Config also didn't work?

nope..

carwiz said:

Boot from your Windows disc and do a repair install.

What do you mean?

I would go in with a boot disk - linux (Mint or an older Parted Magic) would be easier than WinRE - and go to ..\windows\system32\config and rename System to system.old. Then go to the RegBack folder there and copy System to the mother folder.

(That is, providing that Regback\System has a Modified Date predating the problem.)