[Justfishin']

Hope one of you folks can help me-
I had to semi-retire my older Vostro laptop that is running XP (smoothly) and have been given a Lenovo Thinkpad running Win7 Home version, by a client who just got a new Apple IMac (wise choice it seems). I've been using it for my internet browsing, e-mail
My problem-
The freaking screen splits if I move the mouse the right way- but I don't know how to do it or what the right way is.
It seems to happen most when I'm moving it close to the bottom of the window, but sometimes a cross screen sweep seems to do it too.
It''s absolutely maddening!! It will do it over and over when I'm trying to select a page or menu and it will put up two(or more) windows half(or less) size, neither one active until I select one and then it goes right back to the split mode again. It seems that if I double click the one I want, I can work in it- for a while
. I tried google and other searches, looked in the control panel and I can't find out how to shut it off. I tried Ease of Access> Adjust how the mouse works and checked the box that says Prevent windows from being automatically arranged.... but it still does it .

Can someone out there help me to make this #$%^&** thing stop it, please? It did it four times writing this!