I respectfully suggest you retire the XP8 version. Your PC is 64 bit and I am of the opinion that XP8 is 32 bit and is possibly causing an immediate conflict.
On my system I run Windows 7 Home version.
Most of the specs you list will allow you to run a more current version of XP. You haven't indicated what your graphics card is. To run XP you now need a dedicated graphics card. Go for a Nvidia card for better performance.
I would suggest you have a look at the main answer I gave at the following link http://questions.x-plane.com/14139/which-version-xplane-will-laptop-listed-below-flight-training Although it relates to a laptop you could consider the same information for your computer ie check the specifications and then try the demo.
Hope this helps.