To empty the D drive on Windows Vista, assuming the D drive is a partition, find the D drive on the computer, click on "Disk Cleanup Utility" from the "General" tab, and delete any unused or unwanted files. Consider burning certain files to a disc before deleting them with advice from a network engineer and IT specialist in this free video on Microsoft Windows Vista.
Vista, is very similar to cleaning up this C drive on Vista. This is assuming that the D drive you've made is a partition, a physical hard drive, instead of an actual CD or DVD Rom drive, so to clean it up, you would go into the Start menu and go to Computer, and then right click on the D drive, and go to Properties. Once you're in the Properties page, on the General tab, which is the main tab that you see, you'll click the Disk Cleanup Utility. What that will do, is that will scan the D drive, and it will see if there are any temporary files, or files you haven't used in a long time, that are large files. You highlight them, and then hit Delete, and it will delete them permanently off the D drive, to clear our program. Also, you can manually do this. If you have a lot of pictures that you normally store on the D drive, just navigate to the pictures, and burn them onto a DVD, and then simply delete them, after they burn successfully onto a DVD or CD. You can also move them to a thumb drive or an external hard drive, or something like that, to help you clear up space on that drive.