Hi, Craig, I also purchase and use the retail version, I do not like steam.
To use Arma Combined Operations, you have to install the DVD, Arma2 and Arma OA, in the same destination folder, for example; C:\Bohemia\Arma2co\
When the installation of ArmA2 and ArmA OA, ask you specify the installation path, use it, as the example cited above.
1 install ArmA2
2 install ArmA OA
3 install the --->Updates
you want, example, upgrade to version 1.60 and then to 1.62 and finally the last --->Beta Patch
Now you install this --->Launcher
, use this, from my point of view is the best, and configure the path of the executable for each version of ArmA, as shown in that image.
Launcher Tutorial --->VIDEO TUTORIAL
Let me know if it worked for you.