Taken from a Dell forum
you can access your Dell’s recovery partition by pressing Ctrl+F11 when the machine is first turned on. The appropriate time to do this is almost immediately after the power button is pressed. A small message is usually displayed that offers to let you enter the BIOS (usually F2 on newer Dells) or go to the boot menu (F8 or F10, I think; it displays the appropriate key to press).
So, assuming that the partition that the recovery image is saved to hasn’t been deleted for some reason, or that the master boot record hasn’t been altered from the factory settings then the Dell System Recovery software will load and you will be given the option to reimage your drive. Their software is basically just a rebranded version of Norton’s Ghost or some other similar imaging software.
Do keep in mind that if you decide to reimage your machine that all of the data that was on your hard drive will be lost. The machine will be exactly as it was when you first purchased it – meaning that any saved documents, movies, music, settings, programs installed by yourself, etc will be gone.