The best way to re-install the NGX?

I have had to flatten my whole system this weekend, because my system corrupted, network drivers and display driver all died at once.

Well it's not such a bad thing as becasue it is a fresh start. With that is mind what is the best way to install FSX with the objective of making the PMDG work smoothly?

I haven't started installing anyting yet, because I don't want to mess things up too soon without advice.

I have a few questions regarding this.

1. Is it better just to install FSX sp1 and sp2 onto :C drive in admin user and install the PMDG (all updates) here as well? Then just lower the user permissions, to another user called 'flight sim' for example?

2. Or create another user account called 'flight sim' and just do all the installation there, (all premissions granted) ?

3. I have heard also that you don't have to use :C drive defalt location, and that you can use a external drive or partition. I have not tried this does this work?

4. Should I use all the installation .exe files issued over time from PMDG, or should I be looking for a single build from the PMDG site?

I have activesky2012 and VFR scenery to install, but this will come later.

Thanks in advace.

Jools