shell command Excel 2007

[arijit32]

Hello,

I am trying to use the Shell command and it won't start any command line windows. When I run this

retval = Shell("c:\WINDOWS\system32\cmd.exe", vbMaximizedFocus)

nothing happens and all I get is retval =2644. I don't see the command line Window.
Windows applications like this one work fine and open a Calculator window.

retval = Shell("calc.exe", vbNormalFocus)

What am I to do?

Thanks!
Arijit