Page area greatly exceeds the screen capabilities

I installed Client 5 two days ago but a fault developed whereby the page was dramatically enlarged to exceed the screen area making it impossible to use. I tried to uninstall and then re-install but the problem was still there. I tried for the third time and received a message that I could not do this as there was already a license in use. What can be done about this?

could you please send me a screenshot of the enlarged window?