|"I reinstalled my computer to factory settings by the reinstall CD that came with the laptop"|
Kind of difficult to tell. Many Dells have a hidden partition but some are visible. It could be that you are talking about a restore partition.
Most recovery disks can be of a few types. Some do make the cpu just as it was when you bought it. D drive would have been wiped out with little chance of return.
The best thing might be to tell us what the sizes were before and after. If the Cd was a total recovery disk. If you had a D drive when you bought the computer new.
Playing to the angels
Les Paul (1915-2009)