First of all, does that template still exist in /phpBB2/templates/ ?
If so, you should navigate to it's directory, and reupload the .cfg file that came with the theme. Also, make sure that the .cfg file is named "DVDFuture.cfg", without the quotes of course - NOTE: The .cfg name is _case sensitive_.
However, if it is not there, and you were attempting simply to remove it, you will have to do the following (Using this method for simplicity):
1) Re-upload DVDFuture to /phpBB2/templates/
2) Go into the Admin Panel
3) Go to the configuration menu
4) Select another theme that you have installed as the default style, from the pulldown menu, about half way down that page.
5) Go to your profile, and select the style you just chose in the config menu
6) Go to the "Management" menu of the styles section, and press "delete" next to DVDFuture
7) Delete DVDFuture from /phpBB2/templates