Technological assistance sought

Oh feckity feckity feck, I'm in trouble. Work had lent me a laptop as our PC is ancient and fairly crap. Being very foolish, I have allowed The Beautiful Children to use it. Now all the font has become absolutely massive, Eldest Beautiful Daughter has fiddled with it and put the font sizes setting to normal but it still remains massive.

Some of the little x s you click on to shut down (DO NOT FECKIN LAUGH AT MY TERMINOLOGY, I AM WAY TOO OLD TO HAVE LEARNED THIS) anyway, some of the little x's look like the colour has run on them like something has spilled on them.

If you can explain how to fix this in a way my addled brain can comprehend, please please help before I have to fess up to work.

PS
I have been chosen to receive a lovely Busy Bee award from Tom Foolery, many thanks to you sweetie, but due to my complete technological ineptitude I can't show it. It will join my Rockin Girl award from Lisa Q and my Courageous Blogger award from Newfie in my little cyber drawer of nice things. It's not that I don't appreciate it, honest !