This is the fix that I went through.
I have a couple of GTX280 in SLI - previously I had 8800GTX and I could not get any antialiasing working.
It is a bit complex but it does work. I think the problem lies with the predetermined application profiles so what I have done is to remove fs9 from those and then use the Global Settings in the Nvidia Control Panel.
So lets start:
1. Go to C:\WINDOWS\system32 and copy nvapps.xml and nvapps.nvb (if it is present). Paste these into a safe folder - these are your backups if things go awry!
2. In C:\WINDOWS\system32 open nvapps.xml with notepad and do a find for "fs9". It should come up with some text like the following:
<PROFILE Label="MS Flight Simulator 2004">
<APPLICATION Label="
FS9.exe"/>
<PROPERTY Label="multichip_rendering_mode" Value="0x0240000E" Default="0x0240000E" Itemtype="predefined"/>
<PROPERTY Label="prevent_cpl_aa" Value="1" Default="1" Itemtype="predefined"/>
3. Change FS9.exe to
FS99.exe
4. Save it.
5. Do the same for nvapps.nvb
6. Now the nasty bit. In the Run box (Start, Run) type in regedit and hit enter. This will open the system registry. If you are not familiar with this then be very careful what you actually edit. This is the system's view of the software structure on your system. It could be a worthwhile experience to read up on this before doing anything further.
7. In the registry navigate to:
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Video
In there you should see "folders" that are named with numbers like the following - {23A77BF7-ED96-40EC-AF06-9B1F4867732A}.
Open thoe folders and you should see additional folders called 0000, 0001 and video.
In either or the 0000 or 0001 will be a long list of values with names like - _+menu.exe
3DOGL_67207556 or _freedom.exe
3DOGL_67207556.
These are the application profiles from the control panel coded into your registry (thanks NVidia!). What you need to do is find those that relate to FS9 - examples are _FS9.exe
3DOGL_67207556 & _FS9.exe
3DOGL_70835937.
8. Once you have found them, delete them. You will need to go through the numbered folders (e.g. {23A77BF7-ED96-40EC-AF06-9B1F4867732A}.) looking at the 0000 and 0001 folders.
9. If you have numerous ControlSet folders you may well need to the above for them as well.
10. Reboot open Nvidia control panel and make your settings - you should now have AA for FS9.
This has worked for me but it is a drastic move.
Do this at your own risk.
Before messing with the registry take a backup of it and read up on it.
kurt