I have a dedicated storage drive (E) which I use for sample libraries and other misc storage. All my programs are on the C drive with the OS....as well as synths (DLL) and VST's/FX.
Since most synths will load the samples into memory anyway, it doesn't matter where the samples are stored. And since several of the sample libraries I use are in excess of 40G to 80G.... I didn't want them taking up space on my C drive.
As I create and work on projects, I simply store them in the Cakewalk Projects folder that resides on the C drive. It just keeps life simple.
Once I finish with a project....and I'm fairly sure I will not be going back to it any time soon, I will create a new folder on the storage drive and move everything associated with that project to that folder. Then I CUT all the files for it, from the C drive, and drag them over to the storage drive. I then move the new folder into a "master folder" that has a name something like..... Songs_Projects from 2012
If I ever need it, I can find it easily, with all associated files and it's not taking up half a gig or more of valuable C drive real estate.
Before I built my custom DAW, I used a lappy and an external 500G USB drive and stored the samples on it.... it worked quite well.
I also have a USB drive (1TB) connected to use as backup on the custom DAW