FYI : I am using win 7 64bit home premium and have no problems with FSX and haveseveral addon.

Well, the OOM issues seem to resolved for now. I have not upgraded my RAM yet as I am waiting a bit for this to see how things go with add-ons running in FSX and Win7-64 Pro, and also because my system board requires memory of THE SAME SIZE on all slots in order to run all the sticks in dual-channel mode. If I buy just 2 x 1GB to add to my existing 2 x 2GB, the 2 x 1GB will run in single-channel mode. I saw this in the ASUS manual (P5E3-deluxe wifi a/p@n).But I did have a bit of "artifacts" when landing at Mega-airport Amsterdam (aerosoft) two days ago (flying in from Istanbul Ataturk). They appeared around the airport and looked like slim vertical white lines and almost resembled little metal towers or something. And when I exited my runway to start taxiing to the gate, my PMDG 744X completely disappeared! But this was BEFORE I had done any tweaks in the FSX.CFG as suggested by BOJOTE and I had not installed the shader modules version 3.0 yet neither. Last night I did a different flight, to another Mega-Airport - Paris CDG (LFPG) from Antalya, Turkey, and had zero issues. Before the flight, I had setup my FSX.CFG as per BOJOTE's summary of tweaks thread and had installed the shader v3.0 modules. I was running the PMDG 744X, Active Sky Evolution (B614), and Radar Contact. I am still using default FSX mesh and textures. I don't think I will upgrade the textures but I may buy FSGenesis (or other) mesh to improve the geography...I will continue to test. So far so good. John

Just recently I too have been experiencing the OOM errors. I have not installed any new add-ons recently and don't understand where the problem is coming from. It usually happens about 3 hours after take-off from any airport in any aircraft. I have tried the 3gb switch which seems to only delay the OOM crash. My system is a little dated, but runs FSX great so I'd like to postpone the purchase of a new system if I can.Windows XP 32bitE6700 at 3.2 ghz4gb Memory(2) GTX8800 Video Cards (SLI disabled)As mentioned I have the 3gb switch enabled with Userva set to 2560, should this value be adjusted up or down? Currently my system is set so Windows manages my virtual memory, should I select my own minimum and maximum virtual memory values? Do you think the dual 768 MB video cards is choking the virtual memory? Should I remove one card? Would formating the hard drive and installing Windows 7 64 bit take care of the problem? Or do I need to start convincing my wife that I need a new computer? Thanks for any ideas.John