ttmcmurry is correct. But here are a couple ideas from this point forward:
1.) Don't just rely on D-Link's backup function for the router. Create a document with cropped screen captures of all the settings, or at least the most important ones. Are you familiar with, or do you use Adobe's Acrobat? Of course there are other more cost effective versions of .PDF software out there also. But you can create a .PDF of all the settings with screen captures, and make the screen captures there own linked page in the document. It allows you to have an index and jump straight to the setting you need all in a single and convenient .PDF file. Oh, and also copy and paste for mac addresses! I know, a decent amount of work to begin with, but if you plan on having the router for awhile, maybe worth looking into.
2.) If you are concerned about security, save the file in an encrypted container on your hard drive, or a flash drive. On a Mac, this is extremely simple. If you are using a PC, then check out truecrypt.org for FREE software that will let you do this.
Bottom line, it's not as much work as it sounds like. A bunch of screen captures with title's saved as a .PDF file, and stored in an encrypted container for security. Something to think about to make future firmware upgrades less of a headache