> After moving these files I did not gain any drive space. Why?

Try the ViewFolderSize Pro
http://www.moveax.com/viewfoldersizepro/

View Folder Size Pro is a highly configurable program that lets you
keep track of file and folder sizes in real time. You can use it right
from Windows Explorer and get instant and up-to-date information on all
your files and folders. The program is fast, efficient and gives you a
lot of configurable options. The program can show you your disk space
usage as a diagram, making it easy to see. It's a slick program for
monitoring specific folders or for finding out exactly which folders
are taking up the most disk space.