For anyone that is good with a computer, please help.

This doesn't always happen, but, when it does, it's bloody annoying.

Basically, when we open the internet and try to type something, the screen starts going mad and jumping between full screen and small screen (Like hitting F11 alot). Sometimes it will do it when we press the mouse button. The only way to stop it is to hold ctrl, alt, del and close the program. We have to do this about 4 times before it will work and when it does, it still jumps a little when you use certain buttons, EG mainly the backspace.

Any ideas as this is stopping us talk on facebook, here etc etc.