Do I have to uninstall the orginal Sims and expansions in order to install Sims 2?

Nope i have sims sims 2 and sims 3 on my pc all running fine with no problems.....

I'm not sure about the Sims 2 and the original Sims but my computer lets me have some of the Sims 2 games and all the Sims 3 games on it. I think it all depends on how old your computer is, how much memory you have, and if you are going to have all the Sims and Sims 2 games on it. You should probably just try a few at a time and see how it works out or if you have two computers put one series on one of them and the other on another computer.

No. I've got the sims 1 complete collection, all of the sims 2, and sims 3 (with all the expansions) and my computer runs just fine. I don't know what kind of computer you have but as long as you are above the system requirements for each game that you have, it shouldn't matter.

I doubt it. They're 2 separate games.