What method did you use to open a command prompt at boot?
You can type the command below and press Enter to be back at
X:\Sources. Note the space between
CD and
\Sources. It should work fine from either location though.
cd \Sources
It sounds like you may be doing something wrong somewhere. Double check through the steps in the tutorial again to see if you may have missed anything, and that you have followed the steps exactly for where the files should be (step 22) before going to the command prompt at boot.
At step 22, make sure that you substitute the items in red in the command with the correct one for your system.