|Likely the machine's HDD was wiped clean before you obtained it. You should be able to enter the BIOS setup and see if there's truly a drive still there. Should you need any help (from http://pcsupport.about.com/od/fixth...|
Dell - XPS, Dimension, Inspiron, Latitude. OptiPlex, Precision, Vostro
* Press F2 when the Dell logo appears. Press every few seconds until the message Entering Setup appears.
* Older Dell desktops and laptops may instead use Ctrl+Alt+Enter or Del to enter BIOS.
* Older Dell laptops may use Fn+Esc or Fn+F1.