Performance with a closed cloud cover

[W-Natas]

In the noticed that Lock On have now a good performance but when i fly a mission like the Mission 2 in the Su27 Campaign my framerate drops form 40FPS and more to 10-15FPS while im looking to the closed cloud cover or flying into it.

 

I put all the settings in the graphic optoins to the lowest details.

What can i do?

 

My System:

AMD Athlon 2800+

1024MB RAM Dual Channel

Gainward Geforce FX 5900 XT Golden Sample @460Mhz GPU/ 800Mhz RAM

Forceware 71.89

Motherboard A7N8X-E Deluxe

 

Thanks for any sugesstions.