Note. It works fine with Windows 7 as well.
Unfortunately it's not free, but if you are doing open source development they give you it for free. Anyway, the cost isn't sky-high to purchase as well.
If you want to type e1 with 1 as subscript just type e_1. The moment you hit space it will become what you want. To make 1 superscript type e^1 and space. Enjoy!