How do I change the default file manager used in Windows 7?
I just want FreeCommander to be the default, but a general solution is also good.
You need to remember that EXPLORER.EXE does more than just let you move and copy files. It also provides the Start menu, Task Bar, and System Tray. To replace EXPLORER.EXE with another program, edit the following key:
You'll need to make sure to use the full path to the new shell if it's not in the path. Also, I'd try it on a test machine before trying it live. Microsoft usually makes a point of advising that caution is used when editing the registry. This is a case where caution is strongly advised.
The link provided by r0ca contains information for replacing EXPLORER.EXE for just folder operations.