Well since I made this guide quite some time ago, it has become a LOT easier to do. Basically there are now some really neat tools for doing this kind of thing.
First tool I would recommend is nLite.
http://www.nliteos.com/
If you start from your original XP disk (or SP1 or wotever) then this will pick up what version it is etc and then you can apply the service packs to it really easily. If you want you can also add drivers via this program, however for the SATA drivers etc I've found the next program easier.
Second 'tool' is Bashrat The Sneakys unattended packs.
http://www.btsunattended.net/
You need to download the BASE pack, and then any of the other packs you want. Make sure you read the tutorial on the site / in the packs on how to actually do it. It looks like the guides were written before the latest release, as there are a few inconsistences, but it tells you what to do and everything in general.
So basically set up your disk fully with nLite except for the drivers. Then get BTSunattended going on it. Again I'd recommend burning to CD-RW for testing purposes before writing a final CD. Also beware that the more drivers you include with BTSu, the longer the windows CD will take to load them at the start of setup. Also keep a watch on the size of the CD, if you include everything from the CD you will easily exceed 700MB. If you need it all, then you will have to burn to a DVD.
I'm not sure why my guide above didn't work for you with SP2, because I managed it a few times using SP2 (did several different styles of CD), but I'd definately recommend the above tools now over my guide due to the complexity of doing it manually.