This what the .key file says 
[Programs] 
F16gau=DSVTJE5S6DUO 
F16=DSVTJE5S6DUO 
F16.gau=DSVTJE5S6DUO 
As you can see I have tried different ones after F16.gau did not work. 
I downloaded the F-16 panel by Eric Marciano. The file is fullf16pnl.zip and can be found p12 of simvation's fs2002 panel section. I am running fs2004. The aircraft I wish to use the panel for is for fs2004/2002 and suggests the panel by Eric Marciano. In the manual that came with the plane and also the manual that came with the panel it does not say the radar won't work in fs2004. FSUIPC Version is 3.22. I can't see why it won't work, but I hope there is some good infomation here the can help figure it out. Thanks. 
Here is the log 
********* FSUIPC, Version 3.22 by Pete Dowson ********* 
User Name="" 
User Addr="" 
FSUIPC not user registered 
WIDEFS not user registered, or expired 
Module base=61000000 
ClassOptions: UIPCMAIN=FF7F, FS98MAIN=FF7F, FS2KMAIN=FF5E 
WeatherOptions(Orig)=0000B027[0000B027] 
InitDelay: 0 seconds 
WeatherReadInterval=4 
LogOptions=00000001 
DebugStatus=0 
     9875 System time = 04:02:03 
     9875 C:\Program Files\Microsoft Games\Flight Simulator 9\ 
     9875 System time = 04:02:03, FS2004 time = 12:00:00 (00:00Z) 
    26782 FLIGHTS\OTHER\FLTSIM.flt 
    27032 AIRCRAFT\c172\Cessna172SP.air 
    27032 Aircraft="Cessna Skyhawk 172SP" 
    35735 Advanced Weather Interface Enabled 
    52204 AIRCRAFT\VIPER\VIPER.air 
    52204 Aircraft="VIPER vc" 
    64063 C:\Documents and Settings\Jack\My Documents\Flight Simulator Files\UI generated flight.flt 
    64344 Clear All Weather requested: external weather discarded 
    65829 Module identified = "F16.GAU" 
    65829     Illegal read attempt: offset F000, size 2 
    65829Program or module not accredited for use with this unregistered FSUIPC 
    70469 ### IPC Message processed in 4640mSecs ### 
    87469 Module identified = "F16.GAU" 
    87469     Illegal read attempt: offset F000, size 2 
    87469Program or module not accredited for use with this unregistered FSUIPC 
   111454 Module identified = "F16.GAU" 
   111454     Illegal read attempt: offset F000, size 2 
   111454Program or module not accredited for use with this unregistered FSUIPC 
   111813 Traffic File #14 = "scenery\world\scenery\traffic030528" 
   117547 Traffic File #15 = "scenery\world\scenery\traffic_pai" 
   159047 Module identified = "F16.GAU" 
   159047     Illegal read attempt: offset F000, size 2 
   159047Program or module not accredited for use with this unregistered FSUIPC 
   174047 Module identified = "F16.GAU" 
   174047     Illegal read attempt: offset F000, size 2 
   174047Program or module not accredited for use with this unregistered FSUIPC 
   189032 Module identified = "F16.GAU" 
   189032     Illegal read attempt: offset F000, size 2 
   189032Program or module not accredited for use with this unregistered FSUIPC 
   204063 Module identified = "F16.GAU" 
   204063     Illegal read attempt: offset F000, size 2 
   204063Program or module not accredited for use with this unregistered FSUIPC 
   219110 Module identified = "F16.GAU" 
   219110     Illegal read attempt: offset F000, size 2 
   219110Program or module not accredited for use with this unregistered FSUIPC 
   257110 WeatherOptions set, now 0000B027 (timer=0) 
   257235 Module identified = "F16.GAU" 
   257235 ModuleOK="F16.GAU" 
   264125 System time = 04:06:18, FS2004 time = 12:40:02 (19:40Z) 
   264125 *** FSUIPC log file being closed 
Memory managed: 2 Allocs, 494 Freed 
********* FSUIPC Log file closed ****