Merr. I don't need FH+, I would like it, but I don't care. FH works perfect for me. Maybe you should just stop begging, start doing your chores, do extra chores, then after a few weeks of not asking and being pretty much a kiss-up, BOOM ask your mom to let you switch programs. Or:
Say "Mom, if I am really really good for a few weeks, do all my chores without complaining, etc, will you let me switch virus programs?" Chances are, if you approach her maturely, without begging, yelling, and slamming doors, she will probably let you switch virus programs. Parents love it when their children start acting more mature. It means they've done their job right and that you wont come beg for money when you're 30.
Best of luck!