Codes with 20 lowercase characters are for original Ideal Flight 10 and >augmented: example "lkid98fsw872j1cfsr3n" (this is not a real code) for these codes you need original IF10
http://download.codelegend.com/idealflight/Ideal_Flight_Setup_10_012sl.zip
Codes with uppercase: example: ABCD-1234 are for Flight1 registration servers and include IF 10 Special edition for FSX and IF 10 Pro for P3D v3 32bit, and Ideal Flight Pro for P3D v4 64bit:
Go to the downloads page: http://www.codelegend.com/idealflight/download/default.htm