Hi Paul,
yes, some programs can be installed on more than one machine at a time... usually they allow for 2 or 3 simultaneous installs
i never had trouble with activating FSX when my brother was already running a copy on his rig... just today it decided that it wouldn't activate anymore

Cheers
...yet another one of the FSX disasters...

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I don't think we had these Registration/Activation problems with all the previous versions of the MS Flight Sims...FS '98, 2000, 2002, and 2004...
...the registration details printed on the Jewel Case was sufficient...

...!
I just keep re-installing them after each new Hard Drive installation/Format!
Perfect for all the Dads and Youngsters who didn't/dont have access to the Internet for On-Line Registration!
...happy days!.. [smiley=thumbsup.gif]...!
Paul....

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Braging about your FS2004 no problems I see fozzer......
Maybe you should join the group, go out and but fsx. 8-)

I purchased the FSX deluxe Flight Simulator the day it was released in England...
...the same as I have done with all my other versions of the MS Simulators...from FS 5 onwards..

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I use the FSX Flight Simulator for some of my flights, as well as the other versions, but I choose not to regularly join some of the rather humourless, argumentative, and often unpleasant Chaps who regularly appear, and have appeared, on the Sim V FSX Forum since the day FSX was released...

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We have lost a few good Members in the past, because of it...
...trust me!...

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I prefer the peace and tranquillity of FS 2004 most of the time!
Paul....FS 5, FS '98, FS 2000, FS 2002, FS 2004, FSX...plus many other Flight Simulators since the 1970's... 8-)...!
...(...and most of my Scenery Designer, Navigation, etc, programs will not work in FSX).
Win 8.1 64-bit. DX11. Advent Tower. Intel i7-3770 3.9 GHz 8-core. 8 GB System RAM. AMD Radeon HD 7700 1GB RAM. DVD ROM. 2 Terra Byte SATA Hard Drive. Philips 17" LCD Monitor. Saitek Cyborg X Fly-5 Joystick. ...and a Briggs and Stratton Petrol Lawn Mower.