Edwin wrote on Jul 25^th, 2011 at 6:23am:

I'm not sure if it's allowed to install FSX on more then one computer. MS is very picky on licenses and same goes for Windows that officially is only allowed to install on 1 computer at the time and if you to install the same license on another pc, the second 1 is illegal.

I think you are correct in saying that the license is for a single computer.

@Abdulla. If it is installed on your computer, as well as your friends computer, I think MS will, more than likely, view it as a case of software piracy. Maybe you had better buy another copy of FSX, or make your friend buy his own copy, to be on the safe side. :(

Mark