Unfortunately I don't have Norton antivirus, but if Norton antivirus is deleting programs when you run them, that's kind of a big problem with them, I'd think. That's definitely something to take up with them, as we can't prevent them from deleting our installer before it's even run. We use very standard installer software from a major installer vendor (Bitrock Software), so if Norton is going nuts on the files that's something that hopefully they will fix soon.
In terms of activating your key on Steam, that may not be possible some weeks based on our past experience with releases on Steam; three weeks was more standard than on the day of launch for CD key activations. But as-yet I don't have a timeline from them on that particular issue.
And by the way: Welcome to the forums! Sorry it wasn't under a happier issue.