Hi Lewis,
What do you mean by "not showing"? If you get any errors unzipping the archive (which I assume you have the proper tool for), then you should consider downloading it again.
If the download seems to complete but VERY quickly, it is generally a sign it did not work (even if you don't get an error message).
And to answer your other question, it is indeed possible to have two versions of FS, each one with its own FSUIPC installed on the same PC. I am using this configuration but... in this case you should also install FlightLogger twice, in two different folders, and make sure one works with FS2004 and the other with FSX.
Andrei