In my opinion, if you need computer to just connect to the internet, watch DVD movie, office, play games then why pay the extra for Windows XP Professional.
Windows XP Pro will use much more system resource than the Home edition.
I saw so many people use Windows XP Pro and they turn off all unnessary services (mostly networking and security) for reserve the system resources. I ask them why you bought Pro edition in the first place if you don't even use those features? They simply just said they need the best.
I don't see why pay more for the stuffs that you don't need.... Home and Pro are built in the same core. It's exactly the same OS [Compatibility and Stability]
... Don't just buy it because it said "Hey this is Professional version, I'm better than you...I'm the best !!!"
Ask youself if you really need those extra Networking and Security feature of Pro version or not. If you want those extra features then go with Pro , if not then Home edition is just as good as Pro or even faster for gaming with much less in price.