Correct.
I may have found a solution on the UBI support site. I have't tried it yet but (since it is sitting in my copy/paste queue) I'll post it here:
Question
When I try to install the Ace Expansion pack for IL2: Forgotten Battles, I get a message that says it cannot find the Forgotten Battles Installation. I know Forgotten Battles is installed. What is going on?
Answer
If you are having this problem trying to install the IL2: Forgotten Battles Ace Expansion, you will need to uninstall IL2: Forgotten Battles and delete the files and folders left over in the game directory. Then when you go to reinstall IL2: Forgotten Battles, make sure that the auto-run menu pops up asking you to select an installation language. If this auto-run box does not pop up, browse the game disk and double-click the autorun.exe to force the auto-run menu. After selecting the installation language, the IL2: Forgotten Battles installation should continue as normal. Once you have successfully reinstalled IL2: Forgotten Battles, you should now be able to install the Ace Expansion without problems.