As ufotech says you can install multiple instances. Just launch the installer, and you'll soon see a box where everyone just normally clicks 'next' but if you click 'settings' you see the file in its selected directory and all you need to do is add anything to the end of the filename so for example just type 2 or give it a specific name, just adding to the end of the file with no spaces. You'll then see both versions in your program files. Last year I was running 17 accounts from USG.
Going back to my original post on this subject though I would still say something like Social Trader Tools offers the best option
I don't see much point in it, I think it's much more logical to keep the money in several different companies - so it would be much safer, and if you keep all the money in one place but in different accounts, it doesn't make any sense at all.