If you pc has passed its warranty and you can't be bothered to ring Dell then I would suggest the following:
As mentioned in other post, check bios that it is actually beeing picked up.
Check the sata cables are properly attached, moving your pc from "A" to "B" can dislodge them and could cause such an error.
Try using windows install disc to check the hard drive is actually there when windows prepares the setup.
If none of these work then I would suggest getting a spare sata drive from somewhere and plugging it in to see if the problem is the hard disk or the mobo sata controller.