Well, IE's "the page can not be displayed" message is pretty useless. Do you have another browser you can try with? Personally, I use Mozilla for most of my web-browsing needs. When there's an error, it's a bit more informative about what actually happened (or didn't happen).
On the second question, it should be possible to have multiple installations. They'll need to be in separate directories, of course, and you'd want to make separate databases for each of them, but I don't see why there'd be a problem otherwise.