Quoted from another newsgroup (attributed to George M. Winford, MS MVP)
[[Where 2 (or more) drives are involved with more that one partition per drive, the letter allocation by convention is as follows:
C: 1st PRIMARY partition (primary of drive 1 or MASTER).
D: 2nd PRIMARY partition (primary of drive 2 or MASTER).
E: 1st logical drive of drive 1 or MASTER).
F: 2nd logical drive (of drive 1 or MASTER).
G: 1st logical drive (of drive 2 or SLAVE).
H: 2nd logical drive (of drive 2 or SLAVE).
If you do not intend to boot any OS from your 2nd drive, you should actually format your 2nd drive and (when configured as slave - this is important!!!!)
create an extended partition on your slave. One you've achieved this, you'll be able to create logical drives within this extended partition (where you could for example store data etc.).
Once you've done this, you'll notice that you're able to revert back to your original drive letters of drive 1, & that your first logical of drive 2 "becomes E: ]]