If you go through Windows Update, when it's available, you'll get just the bits you need - no updates you already have, no parts that don't apply to you (eg XP Pro vs XP Home). The advantage of getting the IT version is that you can do several machines from it, and you can burn it to CD in case you need to reinstall later (ideally you should keep copies of the really important interim fixes as they are issued, for the same reason, but who is that disciplined?). That way you can have your machine fairly secure before going on-line to top up with any other updates.