Assuming you have XP...
First, you'll have to install the backup utility.
-Put in your XP disk.
-click "perform additional tasks."
-Click "browse this CD".
-Click "ValueAdd/Msft/Ntbackup.
-Install backup utility.
Once you do that, your backup utility is going to be under System Tools
(start/all programs/accessories/system tools)
Click on the backup utility, and that will start a wizard.
-click "next"
-click "back up files and settings"
-tell Windows what you want to back up.
-select a back up location. (drive D, in your case)
-instead of clicking "finish", click "advanced"
-click "next"
-click "later"
-click "set schedule"
-tell windows when it should run backups.
And make sure you TEST your backups once in a while. I've seen simple shadowing fail.