I have done this about 3-4 times in the past 2 weeks.
Ok, make sure you are completely ready to do this. You will lose EVERYTHING!!!
Turn off the comp.
Pop in the CD.
**(if it just boots into XP, something has gone wrong. You would need to enable it to boot into CD rom from the bios, which is simple. I will go into it if I need to).**
It will boot from the CD normally, and you will get a frighteningly blue screen announcing windoze XP installation. Its mmkay. Dont be afraid of the blue.
You want to format the entire hard drive. Its simple to do, as it tells you what keys to press in order to do so. You can either do a quick format or a complete format. I chose the FAT file system, since that is what I always use. I also always do quick format, since i dont see much difference.
Ok, after it has formatted it will restart your comp.
Windows XP installer will appear, and just go along with it, and in no time you will be up and running.
XP normally has all your needed drivers, especially if you are using an OEM cd (such as what comes with DELL or gateway). If not, get em on the net.
There, now dont you feel better? It wasnt so scary!
REMEMBER: NEVER EVER EVER EVER EVER USE AN OEM CD ON A DIFFERENT COMP UNLESS IT IS THE SAME BRAND WITH ALL THE SAME HARDWARE! I just made that mistake on my gateway. I used a dell OEM cd. Now im gonna have to reinstall it ever 25-29 days until I get my hands on a fresh copy of XP/2000/XPcorporate.