How do you restore your computer's settings back to factory settings Dell PC Windows XP?

In a follow up to my last question. The only F keys I have a choice of pushing are F2 & F12. When I hit F12, the choices I have are Onboard or USB-CD Rom Drive. WDC WD2500JS-75NCB3. System Setup. Hard Drive Diagnostics. Boot to Utility Partition. I'm not sure which one to click to restore the computer back to Factory settings. I tried boot to utility partition and it kept saying it couldn't do it or something like that and then it said, Press F1 to retry or F2 to go to System setup. What do I do? Please help.