Lori, I'll second the recommendation for Efofex - it's great software, and the company provides a free 10-year license to students with disabilities. I think the website is
www.efofex.com but don't remember for sure - you should be able to find it by googling efofex.
We're Mac users btw, and our ds uses Efofex. He runs most of the modules under some version of Windows (sorry I can't remember which!), accesses it using Parallels. He does use the module on the Mac side that's available, and another (I think Stat?) just came out in Beta form for Macs which he hasn't had a chance to try yet.
FWIW, he's using the iPad in school this year and he has a nice equation editor on the iPad that he likes just as much as he likes Efofex. I can't remember the name of it either, and the iPad is at school at the moment. If you have an iPad you might try searching in the app store - I think it was relatively easy to find.
polarbear