Hi bosseye,
I am not with Laminar Research;just a flight simmer from downunder.
My understanding of your original question is that you have installed a new drive ( X:/ ) which will be dedicated to X-Plane. Good move. I have done the same.
If X-plane is installed correctly whereby it has not been mixed within other directories eg windows directories etc, it will will be installed in its own directory whether it be the desktop or elsewhere.
Laminar Research recommends that it be installed to the desktop to achieve that "clean" installation. On the basis the installation is "clean" the simple answer to your question is yes.
On the basis you still have a transfer problem, totally delete X-Plane and reinstall the software. The installation process should/will recommend the desktop but should give you the option of an alternative destination. The destination is chosen using the browse button whereby you select the X-drive.
An interesting fact or situation is that X-Plane 10 and X-Plane 11 are totally different software packages and you can run both packages side-by-side on the same drive without one impacting on the other.
In relation to your download time it does seem an extremely long time. My understanding from other download problems raised earlier in this forum it all depends on download speeds, the number of worldwide servers used and where they are.
A tip in running x-plane is that when you start the software to use there generally is an update check process for any files that may have been changed. There will be or is a question or option to check for a beta version. Don't go for this option unless you want see what create a "suck it and see what happens" situation. If you do make sure the beta version is a standalone package otherwise your stable working package will or may be corrupted Personally I don't run the Beta version. I let others, more experienced than me sort out the problems. I only update when a version is officially released.
Apologies for the long comment
Good luck and hopefully you are up and running within minutes, perhaps the hour, of the transfer.
Glenn