You can have as many installs as you like. The trick is NOT to re-install. Simply make a COPY of the entire IL-2 folder.
What you want to do is keep VANILLA version of IL-2 and never actually use it (except to make copies of it). This way, if you manage your copies correctly, you will never have to actually re-install IL-2 again. Just use a fresh copy and go from there.
The only drawback here is HD space. If you have plenty of space (an inexpensive external HD is a great thing to have), you should always have several copies of IL-2 in various forms (versions) as a back-up.
Intel Core 2 Duo E8500
Intel DP43TF Motherboard
3GB DDR2-800 PC6400 Dual
NVIDIA GTX 260 - 896MB
Logitech X-530 5.1 Speakers
24" Acer LCD - P241W
Logitech G15 Gaming Keyboard
CH FighterStick-Pro Throttle-Pro Pedals
GoFlight GF-T8 Module