This is caused by a "\" at the end of the variable value for, in this case, "C:\Program Files\Support Tools". These are the steps to correct the problem in this case:
1. Right-click My Computer and press Properties.
2. Select the Advanced tab.
3. Press the Environment Variables button.
4. Double-click PATH in the System variables area.
5. Remove the \ from the end of the string.
6. Press OK and OK.