Start by right clicking on your desktop and choose new and create a new shortcut to cmd.com. Then right click on the shortcut and choose run as administrator from the popup context menu. Click OK if you get any security warnings.
When the command C prompt appears type the following in the window:
For a 64 bit version of Windows 8.1 type:
then press the return key.
For 32 bit version of windows type:
then press the return key
That should resolve the problem and Classic Shell should work properly. If you don't know what version you are running right click on your computer icon in the start menu and choose properties to get your windows version.
Be sure you go into the advanced settings of Classic Shell and set it to skip the metro screen if you want to boot to the desktop.