I don't know why anyone would want to do this, but you can change the key used to complete commands from the prompt (tab by default in XP and Unix.)
In [HKEY_CURRENT_USER/Software/Microsoft/Command Processor], set "CompletionChar"=dword:00000009
to the ASCII value of whatever key you want. Adding this key also allows tab completion in Win2000.
More on tab completion
Posted in Windows XP by Community Submission