Since FSX is a 32bit application it will not address any more memory running under 64 bit Vista ?I seem to recall NickN suggesting an x64 OS for FSX for memory gains?http://www.simviation.com/cgi-bin/yabb2/Ya...=1197380641/0#2Yet according to:http://zone.ni.com/devzone/cda/tut/p/id/5709"Operating systems such as Windows Vista x64 Edition are not automatically faster than their 32-bit counterparts. In some cases, they may even perform slower ... Emulated applications running within the Windows on Windows 64 layer (discussed in more detail later in this article) will not be able to address any more memory than they could on a 32-bit system."

You can use more system memory with x64 OS. I wish I had 4 GBs of memory sometimes, by 2GB gets eaten up easily in xp 32bit.

The additional memory capacity that you have left over after FSX uses what is able to is where you will see the performance difference. Many different things are using memory on your PC when you are running FSX (or anything else for that matter). So, even if FSX is limited by the amount of memory it can use, there will still be plenty left over for other things running in the background. This is especially useful when you are running several different add-on software while you are running FSX.