In easy radarmode I can't acquire a lock by using the insert key function. I can select the target and mark the target on the radar screen, but no yellow diamond box appears and it's not possible to fire a radar guided missile.  
  
I always have to wait, until the programm automatically locks on the target and the red box appears. After hitting the target I have to wait until the aircraft crashes into the ground to get the next target acquired automatically. 
  
It worked fine without having patch 2 installed. I have made two clean new installs of the game and tried it with several aircrafts. but no way...  
  
I play the german version. 
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Athlon XP 3000+,  
A7N8X 2.0,  
1024 MB RAM, 400 Mhz Infineon,  
Sapphire Radeon 9600 XT 256 RAM (Ati Catalyst 3.7),   
DirectX 9.0, 
XP prof. sp 1, 
1024 x 768 / 32