Terrible! Somebody stole my system prop.

I tried everything I can imagine but no result. Suddenly I discovered that when I should click on Windows update I came to a website telling me in two sentences that I could update my mac there. Somebody have been inside here and mixed up almost everything. I managed to fix several things but the problem with windows update and that system restore is gone I don't know how to fix, Is it possible at all??? I went down and looked in my registry too but with no result. Please, if someone out there know something about this problem contact me!