To do this, crank up your registry editor and go to HKEY_CLASSES_ROOT\Directory\Shell. Right-click on Shell and create a new key. Type in an appropriate name for the key. On the right pane, double-click on the Default value, and add a title with a & character in front of the letter as an accelerator key. Right-click on the key you just created and create another key under it called command . For the Default value of command, enter the full path and program you want to execute in the Value data box.
For example, if you wanted Notepad, you would add that as the first key, the default in the right panel would be &Notepad so when you right click on the Start Button, the N would be underlined and you could just press that key. The command would be something like C:\Windows\notepad.exe. Now when you right click on the Start Button, your new program will show up.