Backup any data you need to keep first.
Here are the instructions :
Dell - Support
If they don't work for you, you have two options:
1. Boot the Dell dvd and reinstall using that ( if you have one)
2. Mark the Recovery partition active ( sometimes called Flagged On ) and restart. The recovery program should start .
To Flag On the recovery partition , you would use a bootable partition manager, GParted is a free one here:
SourceForge.net: GParted: Files
It downloads as an .iso file.
Burn that .iso to a cd - do not format the cd.
Use this .iso burner :
Boot the cd you just made -it will load into memory and show your Hard drive.
Rt click the recovery partition ( it will smallish 6-10GB) and select Flag On , then click Apply.
The recovery partition should now say "boot" next to it.
Remove the cd and restart the pc.