What do you mean by primary storage drive? If you're talking about where your programs store documents and data by default, you'll have to move your My Documents folder.
Open Explorer (Windows Key + E), then go to My Documents. Right-click on the empty near your files. You'll see "target location" or something similar, and this is where you specify a folder on your secondary hard drive.
Even after you do this however, you may have to move your old files to the new folder.