It is possible to have two browsers. I have both IE6 and Opera6 on my system (although there is a newer version of Opera I haven't bothered with this - I am of the school of thought that if you are happy with what you've got why change it!).
They both co-exist quite happily with each other and although I prefer Opera (it seems to be faster than IE), some websites don't seem to so I then switch to IE.
I use Netscape as you have more control over cookie Security and pop-ups. Got IE6 on comp only because I have software that likes to see it there, and gets upset if it cannot see it when loading programs. Netscape for me as less bugs, I was forever having to repair IE