After you renamed your 1,2 version you can run the disk and uninstall IL-2 1946. It won't remove your renamed version. example Mod Il-2 Sturmovik
After you uninstalled then the option to "install" will be there.
_________________________
Intel core I7 950 @ 3.8
Asus PT6 Motherboard
6 gigs OCZ DDR3 1600
Asus GTX580 Direct CU II
60 gig Corsair SSD [with only COD and dual boot OP system]
500 gig HHD
LG 37" LCD
MSFF2 Joystick
Cougar Throttle
Saitek Pro Rudder pedals
Voice Activation Controls
Track IR 5 ProClip