Building new unit and my computer guy is saying to use Win XP Pro as it is system recommended.What about availability of DX10 with XP Pro?Thanks,Ron

DX10 will not work with XP and only compatible with the Vista OS. To get DX10 to work with Vista, you'll also need a DX10 compatible video card. Hope this helps.Best regards,Jim

I don't understand DX9 DX10 and what they do.It just looks like if I am building a computer for FS I need to be able to utilize DX10 and maybe eventually DX11 etc?Thanks,Ron

A lot of people are just as confused. The only suggestion I have is that you visit Phil Taylor's Blog (ACES Team - Creators of FSX) and review his comments concerning DX9/DX10 within FSX now and in the future: http://blogs.msdn.com/ptaylor/default.aspx. There are also several discussions regarding DX9/DX10 in the FSX Forum on AVSIM. A forum search will bring these threads up for your perusal. I upgraded my system to Vista/Nvidia 8800GTX video cards to be ready for DX10 capabilities and a bit disappointed I may have to upgrade again for DX10.1. Yikes!Best regards,Jim

For FSX, XP Pro is an excellent choice.Maybe some time in the future, Vista will bring us new and exciting features, but that could be years away and by then other new hardware will be available (and possibly required) to run it.