how new is your mobo, older ones might have issues with large drives.
What do you mean by the 2TB drive is not working properly? if you mean it is not automatically giving you more disk space then thats OK, because thats not how it works.
Currently steam sounds like it is installed on C:\programs\steam or similar, you need to backup your games, to your d:\ reinstall steam on d:\programs\steam and then restore the backed up games.
Unless you tell a program to install on the D:\ (i.e. the 2TB drive), then it won't install there. Hope i'm not teaching you to suck eggs, but your description of the program 'doesn't seem to be working' needs expanding on to help us help you without starting at the basics.