My system is an I7 940 on an Asus P6T Deluxe motherboard with 4 GB RAM and an ATI 4870 1GB video card. I run FS9 with Windows XP SP3 32 bits. I use my desktop exclusively for FS9 and my hard drive is perfectly defragmented and I have of course the 3GB switch set.I usually fly PMDG 744, PMDG MD11, CS757, LDS 763 with many detailed scenery add-ons, REX textures (512 bits), and weather on ASE.Until I added REX, I enjoyed very high FPS and no CTD. After I installed REX, it appears my system has difficulty coping with the load. The most recent occurrences were a system shut-down and reboot when on short final at WSSS (Imaginesim scenery), and a CTD when on final IGS13 at Kai Tak (FlyTampa scenery), both flights on the PMDG 744.Could anyone suggest if there is an obvious hardware upgrade that should be made on any of my present components?Thank you for your help.

Jean-ClaudeYou need to check your RAM on an i7-940? it should be Triple Channel DDR3 in the correct slots in a configuration 3 x 1GB, 3 x 2GB, or 3 x 4GB (or 6 x 2 GB, 6 x 4GB if the mobo supports it. With just 4GB on board your system is unbalanced. You also need a 64-bit OS as with any complex plane and/or scenery you will definitely get OOM errors using WinXP 32-bit. The /3GB sitch and the USERVA switch do not always work. The problem is that you have very little virtual address space (nothing to do with physical RAM) for FSX and addons and video card to load into (max up to 3GB) but on a 64-bit OS you get a full 4GB. Unfortunately, your video card will throttle that cpu - you really need an nVidia 470/480/580 for best results or at least an ATI 59xx (possibly 69xx) series.So - my advice - check your RAM and upgrade to a 64-bit OS - Win 7 works very well. :Sleepy: RegardsPeterH

Thank you Peter, your advice certainly confirms what I suspected regarding the OS... and the nightmare of re-installing my huge FS9 collection of add-ons both planes and sceneries!!!I will check the RAM setup as well but since I bought my PC from a specialist store, I would assume they did their job right, well never assume.With best regards from Switzerland.