Lewis,
When you want to save one of our downloads, you can save it anywhere, so for instance you could save it to the Desktop or some people create a special folder on their C drive called "Downloads" so they know where everything is. Then, once the download has finished, you need to go to wherever you saved it (the desktop or your new "Downloads" folder and then double click on the icon for that plane. A box will open and you need to click on Next and install the plane in your Flightsim.
For FS2004 this will normally be:- C/Program Files/Microsoft Games/Flight Simulator 9
For FSX I'm not sure as I don't have it!
As long as you follow this guide, the plane will appear under EuroHarmony (or EuroHarmony v4) in your Aircraft selection window (in FS2004).
As for your pilot ID, this should change automatically - I'll ask one of our Technical Team to look at this and see what your permanent ID is and then we can change your Forum ID to match so you won't have to leave, ok?
So just give us a short time to sort out these details and then you'll be good to go :8