Hello timbo, CFS3 on 64-bit Win7? Good choice, I've been running it on the 64-bit version since the pre-release editions of Win7.
If you're looking to install MAW, PTO, ETO, Korean Skies then you'll need a 'clean' install of CFS3.1a. That means
no add-ons, just get the patches from Microsoft and apply them. Make sure you do 3.1 update first, then 3.1a and fly the sim in Quick combat between each step.
Let's say you then want to add various aircraft and effects to the sim. I'd suggest you make a copy of your 'clean' CFS3.1a folder, rename the folder appropriately and
then get MultiCFS3 from Martin Wright's site. Unzip the file, place MultiCFS3.exe (
not the unzipped folder) in your newly renamed CFS3.1a folder and run it. Once that has successfully run you can then fly the new copy of the sim, as well as set the config. There's an illustrated guide to doing this in the ETO Installation guide, see the sticky above.
This leaves you with the original 'clean' 3.1a, plus a new copy which can have the effects, NEK, weapons packs, whatever added to as you please.
The 'clean' CFS3.1a is left strictly alone after this and can be used for making other
working copies if you wish. More importantly: MAW, ETO, PTO, Korean Skies can be installed and you have a 'clean' CFS3.1a in the default installation location for them to find and install from. Each will create a separate installation all by itself, they do
not live together in a single CFS3 installation.
In case anyone is unsure what MultiCFS3.exe does, it only enables a
copy of CFS3.1a to run independently of other copies. It does
not make copies of your CFS3.1a - you have to do that yourself.
Using MultiCFS3, you can have various installs which have different configurations, different screen resolutions, different scenery, lighting, colour settings and they won't conflict with each other. If you don't use it, all your different installs will share the same settings - change them in one and they're all affected the same way.
Currently I have five different installs and they all live happily together. Clever chap, that Martin Wright!