Look at the example discussion at http://forums.cnet.com/7726-13974_102-5325452.html?tag=posts;msg5325452
Call Dell and see if they have an OS for you to download or buy. It will be much cheaper (about 35 bucks) than the other methods of getting Windows.
You can also install UBUNTU if you can't afford the prior answers.
Bob
Hey, my dad gave me his old Dell work laptop and i want to wipe it so it doesn't have the work login or anything. I want to restore it to factory settings.
Its running Windows XP and I don't have a cd with windows on it.
Can someone please help me?

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic