Is that possible to install on an external HD to use the game on various computers?

Yes, you can even put this game on a usb drive or thumb drive. I think that's slower though.

yes but i think you need to reactivate after unplugging and plugin again

Quote from baSh0r :

yes but i think you need to reactivate after unplugging and plugin again

Already tested. No need to reactivate after unplug!

Thanks. Alreay instaled in a pendrive. In few day will post my experience with it.

Quote from Amadeu Jr :

Already tested. No need to reactivate after unplug!

You'll only need to reactivate the licence if you plug it back into a different PC.

Yes, I tested it right now on my laptop.

Sorry to bother, but when I last tried this and then clicked the lfs icon I got a message saying " incorrectly installed on harddrive"?

It's worked for me on computers in our school!

Quote from Ricerguy :

Sorry to bother, but when I last tried this and then clicked the lfs icon I got a message saying " incorrectly installed on harddrive"?

You usually get that if you didnt copy the data directory correctly.