Pre-Open-Beta Issue 3: 32-bit Win 7 / Vista users with 4GB of Ram CAN make their experience much better by using 3GB switches
This issue is that in spite of what's installed in your machine, any 32-bit version of Windows actually can only use 2GB of User Mode RAM. Through some new uses of DXT compression we have been able to cram down the requirements to about 1.7GB to 1.8GB of RAM, but depending on the setup of your 32-bit machine - this might still cut it far too close to the limit to be stable (and leads to crashes and instability in some setups). The answer (other than installing 64-bit Windows which is the best solution) is to utilize the 3GB system switches provided in the new Windows versions (which on Win 7 and Vista are actually NOT called 3GB switches that at all). Autodesk has a very similar recommendation on their side for intense applications like AutoCad and 3D Studio Max:  http://usa.autodesk.com/adsk/servlet/ps/dl...&linkID=9240697

So while this is certainly a hard-core tweak (it requires the bcdedit /set IncreaseUserVa 3072 command to be run from the command prompt as an Administrator - and if you have no idea what I am talking about, you probably should not try it), those that have used it now report that they have gone from crashing 5 times an hour down to not crashing for several hours. The reason is that when the game uses 1.8GB of RAM, you have VERY little left to run anything else (Virus-scans, or even just more components of the operating system), so by enabling the memory to use all the way up to 3GB of memery (with the last 1GB reserved for O/S and Kernel) you can perform much better in the game. HOWEVER (and this is key), once you do this, your O/S or Kernel COULD become unstable, if you have far too many drivers or other components loaded (or just crapware on the machine). But on a reasonably clean machine, this is a pretty harmless tweak (but again - do NOT attempt this unless you fully understand what you are getting in to).
http://apbreloaded.gamersfirst.com/2011/05...own-issues.html