as you can see and as I pointed out to Vic... more is not always worse and less can be worse than more in FSX.
It sounds to me like everything is working correctly but you are held back by that Dell system
The only thing you can do with the current system would be to upgrade the memory to 2x2GB DDR2 800 CAS3 or 4 MAX which would help but you also have to find out if that tower will accept 2x2GB in the slots.. it may not
That would assist but you are still held back by the motherboard. If you could get that proc to 3.6GHz it would go a long way too. They will do 3.6GHz but it requires a 1.44-1,46v vcore and a HSF that can handle that load.. you also must shut down the CPU speedstep and other CPU features such as CE1, Vanderpool, etc.. all the CPU power management features in the BIOS must be shut down.
Did you DISABLE the UTX 'moving traffic' feature to see how much of an impact that was having?
Another thing you can do is replace the default AI with WOAI airlines and GA traffic from a few sources. Its not an easy job and it has to be done right by disabling the FSX aircraft traffic bgl file correctly and also updating the WOAI and GA traffic BGLs to FSX using a special converter tool.
Removing the high poly AI load in AI and raising the AI sliders can help but as I said it is quite a job to accomplish
I assume there are no partitions on this 500GB hard drive... if there are, and you are not running FSX on the 1st partition installed directly into Windows that will also slow you down quite a bit. Best way to run FSX is on its own drive with no partitions but baring that, Windows and FSX should be on the same drive and located on the 1st partition if a partition exists on that drive
The same system that would do best for video editing will do best for FSX with one exception... in video production you want a RAID array which uses 16K as a STRIPE or BLOCK size and in FSX you want a RAID array that uses 256K to 500K for a STRIPE or block size and in BOTH cases you do NOT want to use motherboard RAID0.
A professional RAID0 solution is the key...
http://www.newegg.com/Product/Product.a ... 6816116042 one that will allow you to set up 2 arrays, one for editing 16K STRIPE) and one for FSX (256K STRIPE). In both cases the best drives for such purposes would be the Samsung 32MB cache 500GB drives or the WD Raptor. The newer Samsung drives are much cheaper than the Raptors however because they are being used in RAID0 you can take full advantage of the 32MB cache and those Samsung drives are better suited for AV production in small STRIPE RAID when used in RAID.. as single drives they are not fast, only in multi drive RAID systems with those 32MB cache Samsung drives perform equal or better than a Raptor.
With Nehalem hitting the streets next month I would wait before building.. after the first of the year you will have a much better choice for upgrading and the expense of DDR3 can go into a i7 platform where it belongs so you get the full DDR3 perf ability out of the cost.