windows 7 - Combining two physical drives into a logical one

I currently have a 1TB hard drive when I store all my media - music, movies, etc. It's getting quite crowded so I want to buy another hard drive. However, I would like to add new space to the current drive and not create a new one (i.e., all the files should be under drive letter Q, for example).

Is there any way to do this?

EDIT: to clarify, the drive I store my media in (the one I wish to expand) is not used for anything else - Windows is installed on a different drive.

EDIT 2: Also, the drives are not the same size, if that matters.