I don't want to close this thread, but I feel I must point out that, according to the EULA, you must have purchased a separate copy of the game for each machine you install it on (unless you remove it from one before installing on another).
I don't have a copy of the EULA handy, but that is what it used to say, at least. If someone can prove me wrong, I'm more than happy to withdraw that statement.
The EULA does specify this.
FWIW, the EULA is at best nonsensical, at worst contradictory, regarding CD/DVD use, since the EULA is contained in the 3.19 patch readme, but still prohibits running the game without the disc, which the 3.19 patch made unecessary.