Burning a cd-rw from my non i tunes library

Never heard of that before.

You can change the CD/DVD drive letter as follows, but D may already be in use by some other storage device:

Control Panel > Admin Tools > Computer Management > Disk Management

in the bottom-right panel, find the ribbon which represents the CD/DVD drive.
Right-click the box on the left which shows it's drive letter.
Choose "Change Drive Letter & Paths"
Click "Change" and choose the letter 'D' (if it's not available it means 'D' is already being used by another drive).
Click 'OK'