Which IL-2 are we talking about? Old 1946, Cliffs of Dover or BoX.
IL-2 1946 works as far as i know with the "no DVD patch", I had it installed on my system previously.
IL-2 CoD needs TF mod to work as of now. Will probably be addressed with TF patch 5.0 since they have the source code now and are licensed to work with it.
IL-2 BoX works out of the "box".
But I might not understand the question properly?
EDIT: Had to test IL-2 1946 just to be sure (have a complete copy of the game on USB drive) and it ran fine even from USB.
You can just download IL2 1946 off Steam. Once you've done that, move the IL2 folder somewhere, then delete Steam. Works perfectly. No CD required. $9 or whatever Steam charges, beats dealing with headaches trying to get the disk version to run.