from what i remember Xp home doesnt have the facility but XP pro does..AS long as you have the XP disc (s) it shouldnt be a problem , the only thing to back up then would be any files, photos etc. these could be saved to CD/DVD anyway if they were that important
To be honest as a novice i wouldnt lose any sleep over it just yet, think you need to find your way around the PC first and feel comfortable with it...