XP Pro is more orientated towards the business environment, & has more on networking. As a matter of personal preference I prefer it to XP Home.
Loading XP with Vista already installed will cause problems, I think you have already ben advised on this matter in another post.
I refer you back to my postings in the previous message you listed.
Additionally make certain you have the SATA drivers for your HDD for XP before you start. If you haven't got a floppy drive you may need to burn them to a CD.