Help

I have windows vista. I had mozilla firefox but now Internet explorer shows up. I am so crazy trying to get firefox back. don't know what I am doing.
If I am online I can click on a web site someone puts in a thread. but when I get an email with a site to click on, nothing happens.
When I click on my "bookmarks" it takes me to join yahoo .
I miss my bookmarks.

Some of the shortcuts I have on the monitor doesn't work.
I tried to reinstall Mozilla firefox. didn't work. Am I supposed to "run" or "save" when installing . Hope you can help this old person.
I do have Norton. Thank you so much.