Can't open a folder in windows 7 by double click

Can't open a folder in windows 7 64bit, by double clicking, it shows me that the default option for opening folder is "cmd" (it's highlighted when i'm right clicking a folder, and the "open" option comes next). I've tried running some registry fixing tools, but it didn't fix it. Can someone suggest me what should I do.

Set HKEY_CLASSES_ROOT\Folder\shell\(default) to an empty string.

Yeah !!! Solved it!!!!

in the regedit I've entered to the HKEY_CLASSES_ROOT\Directory\shell\, there was a sub directory called cmd I've deleted it and now everything works fine.

I think it didn't do any other unexpected damage, I've been using my computer for several hours and it seems there are no unwanted side-effects

An anonymous editor mentioned that deleting subdirectories might not be necessary, he rather solved it by changing the value of (default) to explore (which picks up the explore subfolder instead of the cmd subfolder).

This worked for me!!

Open regedit and change the '(default)' value to 'explore' in the next two lines (no quotes marks)

HKEY_CLASSES_ROOT\Directory\shell\

HKEY_CLASSES_ROOT\Folder\shell\

I've solved it simply by renaming the folder. I could access 99% of folders but for some reason one or two wouldn't open. Only downside is, if I rename it to what I had before, again the folder doesn't open.