"Where's Command Prompt in Win-10 Tech Preview?" - Answer is....

...It's right here! It has a new icon, and a new name, Windows Powershell, but it's still doing the same old jobs you did with Command Prompt. And as you see, you can use it to run DISM.exe to clean up and restore your system image, just in case you'd like to do that. And if you want to find out everything that can be done with the Deployment Image Servicing and Management Tool, just open Windows Powershell in Administrator mode, (as above) and at the cursor, type in as follows: DISM.exe /?
 
You'll get a grand list of everything you ever wanted to know about it, so be ready for some reading....you may want to make a screenshot of it.