Command prompt not working
When you state the command prompt doesn't work, I will assume it fails to appear since you were being so nice to say hello and all, you forgot to say what the problem is.
Here's my fix:
Read all of this and when you get to the red part, Copy (Click and drag through, turning it all dark blue) and then right-click the dark blue part and select "Copy." Now, open Notepad and in the screen area, right-click and select "Paste."
Everything I put in red should now be in notepad, but in black now. Click "File" and "save as" and give it a name and a period and the the letters "reg", any name will do as long as it ends with .reg
Right below where you typed in a name, there is a little triangle, click it and select "all files" and then click "save."
Now go to where you saved it and double-click the file you saved. A message will appear asking if you want to merge the contents into your registry, click Yes.
Now, anytime you are in Windows Explorer, you can right-click on any folder and the Command prompt will be a selectable choice. It will appear and even have the full path already entered to the folder you right-clicked.
This is not a fix for your missing CMD windows from the start menu, it is actually better, nothing to type.
Windows Registry Editor Version 5.00