if you have the power then yeah. Thats what i do on my home PC so i can reinstall/reghost my OS. Or you could just partition a drive but i am not sure is this a good idea.
A good approach maybe to use a small fast drive for the OS and then a lower power consumption drive for the mp3s etc. Also, if you put your media drive in a removable caddy or have it in a USB2 or firewire enclosure you can remove it and hook it up to your PC to transfer files