I have my own professional opinions about Norton's software, but the most recent version is certainly much better than the last several years... Regardless, no matter how good the security software, it can still cause some pretty bizarre issues at times--and that's because it's so deeply integrated with the OS. Sometimes when you hit a brick wall, the best thing to do is try running the computer without the antimalware and firewall software (in fact, I'm helping another user in a different thread at the moment and we're attempting precisely the same thing just to try and pinpoint a cause).
As for reinstallation, your steps are correct; the only issue might be if you do not have access to the original installation executable. I personally am not sure whether it's possible to download a trial version of Norton from any number of download sites out there and then enter a serial number to register it, but I would assume it is since nearly every security suite works that way. If you aren't comfortable doing this you absolutely do not have to, but there are few other things that seem necessary to check at the moment.
Plus, here's the thing: even if we get to the point where this doesn't work, it's probably a good idea to uninstall it before performing a repair install (in-place upgrade) on the Vista installation anyway. Since you currently have access to Windows, it's always a good idea to remove security software before performing such intensive repairs on a system, just to eliminate possible hang-ups during the install.
I know most others who have taken part in our four-page discussion here now agree that a repair install seems to be the only truly logical next step, but short of speaking on their behalf, I would think most techs would suggest the same step I am here regarding Norton (and any security software for that matter) if repairing the OS is not yet an option at our disposal. It isn't the end of the world if we end up stuck without Norton post-uninstall anyhow; you can always take that up with their support team at a later date, and in the meantime, as we try to get this situation corrected, you can go back with any of several free solutions which happen to offer statistically superior protection anyhow.
I hope this makes sense. I am not by any means suggesting that I am confident that removing Norton will fix anything, or that you will experience any sort of problems trying to reinstall it. But all I can do is offer suggestions from an experiential standpoint as a technician.

~os