Will Flight Simulator X run on a desktop with Windows7?

Yes although the demands of the programme if you use the steam edition are slightly different -
basic requirements;
Operating system Windows 7, Windows Vista, or Windows XP Service Pack 2 (SP2)
Computer processor 2.0 gigahertz (GHz) or more
Memory 4 gigabyte (GB) or more of RAM
Hard disk space 4 gigabytes (GB) available hard disk space