Your disc may be bad--try just copying all the install files to your hard drive first, then running the install from there.
Barring that, if you registered the CD key with us back when you got it, you should have an account (the same as then) with GameStop (they bought Impulse a couple of years ago, which was our digital distribution platform) to be able to download the game in entirety.
If you can't locate your account there, the game doesn't show up on it, or never registered the game, please contact support@stardock.com and they should be able to help if you do have the CD key.
