What kind of computer do you have? and what kind or restore media do you have. . . alot of newer computers have a partitioned hard drive with a recovery image on the second partition.. others come with restore disks and others come with a windows XP cd. with seprate driver cd,s//// most anyway you look at it you are going to lose all of your data... your best bet is to just back it all up onto a cd, antoher computer, a usb pen drive or something of the like. . then you basically are going to boot off of your operating system cd smack the space bar to boot from cd and follow instructions. . .
ther eis a good tutorial here
http://www.theeldergeek.com/clean_installation_of_windows_xp.htm
basically you are going to delete your partition, create a new one, format the drive, copy files, install xp and configure it. . . . is fairly simple. . . . Xp will probably pick up and install most of your devices but you will probably have to manualy install a few of them.. .using there install disks or you can download the newest version of them from the mfgr's website. .
pm me if you have trouble I own a computer shop and have done this daily for the past 7 years . .
good luck
chris