Trout, I have no experience with 64bit, so I can't say for sure.
Now that's not entirely true.
Just last week I was over at a local friends installing this game, on his Vista machine.
It wouldn't start the game any version.
I tried the Net framework, it did as you said, I just ignored it, and took it for its word.
I then did a search and found out that Vista requires Il2, and I guess allot of things to be placed outside of Program files, in a separate folder for them to work.
So I did just that, made a new folder in C drive called Games, and installed IL2 in it.
It worked like a charm.
He wanted me to fix his CFS1 while I was there, I could get it to install, and run, but it would not see his joy stick.
It works in all of his other games, including IL2, weird too since its a none FFB Microsoft stick.
So yes do as FT told you or follow my format.
You might get lucky.