Full install of WinXP

Hi, I’m hopeing someone will be able to give me a quick answer to this basic question. Currently running Win98 and I want to do a full/clean install of WinXP Pro. I will have to format the drive and then do the clean install. Is there anything else that must/should be done to make this as clean an instal as possible. This particular machine had NT4 oem on it initialy, but was formated and Win98 installed and I believe there are NT files lurking around cause it just dosent run nearly as smoothly as I believe it should be, I would like to ensure all system previous OS files are in fact deleted so that a clean install can happen. What steps should I do to make this a reality?.
Many Thanks for you assistance with this.