I looked in the installed programs in the control panel, and it wasn't listed. So I re-downloaded from amazon, installed and then it asked for the key once I started the program. And the Key failed - same error - too many times and/or to many computers.
I contacted Amazon requesting a new key, and they pointed me to 2K, since they are the only ones that can issue keys.
Well, actually, that worked out pretty smothly. A few screen shots of my purchase receipt, activation key, and the error that I get. Few hours later, 2K Support issued me a new key (Steam version, though).
So, I downloaded it (again), and was pleasantly surprised that it was the patched version. It was a vanilla copy, but fortunately, still have the mods saved.
Thanks for the suggestions/help!