enter bios (not sure what key it wil be to enter bios on a dell but it shoud say when you see the dell logo when first turning on)
once in bios make sure that you hard drive is set to boot first. if you not sure how to do this just load the defaultsettings (it will say somewhere at the sideor bottom which key to press for default settings) save then exit.
failing this try restoring the laptop with your recovery disks
if it will not restore might be a faulty hdd. but these are very easy to fit and install if you need to buy a new one
Tomlad
June 2010