Anna if it constantly changes and you did not click on anything to allow it to change it for you, then you may have a virus of some sort, or a program that is running on your machine what you may have picked up by accidently clicking on something while you were surfing. Just to be clear, the virus that I mention may not be harmful beyond changing you homepage.
A couple of questions:
1. When you open your browser and it goes to the wrong homepage. Go to the tools menu > Internet options. The first tab will list what IE should be going to, is it what you want.
2. If you click refresh does it take you to your home page or back to the wrong on.

We'll start there.

wolfsoul I think that yours may just be a cache thing. Go ahead and clear that and your cookies(Make sure you know what that does). I would have to know a few more things before making any more guesses.

Go ahead and post back into this thread, if you like or PM me. IF you post back into this thread, let me know through a PM. I almost missed your 2 questions.