This question already has an answer here:
I once read somewhere that NTFS drives performs better as a single big partition. In Unix systems however a separate HOME partition makes sense; they are convenient for backup-restore actions (without disturbing user files).
Under Windows, a separate drive for storage (multimedia and such) needs further tweaking like changing environment variables (Program files), default paths (My Documents, My Music ...) etc. The idea of isolating the system files sounds good, but are they good for backup options? Will the two partitions affect speed and performance? A friend of mine keeps a PC with four partitions in a single HDD, but he didn't explain to me why it is useful.