It is likely due to your environment variables. Here is what I suggest:
- Click Start Menu
- Type sysdm.cpl into the Search programs and files (do not hit enter)
- Right click sysdm.cpl and select Run as administrator
- Go to Advanced
- Click Environment Variables...
- Double click Path from the System Variables list (after scrolling down)
- Select everything in the box Variable Value:
- Hit CTRL + X to cut the values, leaving it blank (you may have to put a space in), and hit OK.
- Hit OK again to close Environment Variables to reset the Path to nothing.
- Now, click Environment Variables... again.
- Double click Path in System Variables (after scrolling down again)
- Paste the values back into the path Variable Value by hitting CTRL + V.
Does command prompt work after the above process?
If not, do steps 1-8, but use CTRL + C instead of CTRL + X (do not leave the path blank this time in other words), and paste the path in your next post. You may be missing important variables.