Itunes on home PC not working properly

My home computer runs Windows 7. I have an iphone 4s, ipad and ipod that I connect to this PC. My problem is I can't get itunes to work anymore. I've tried uninstalling as has been instructed here somewhere but it still doesn't work.

It opens up the screen goes black & then seems to change & itunes displays with a huge font & all fuzzy. It says to change the resolution etc but when I try to do that it just goes back to my computer desktop. Is there something else I can try to get it working again? Luckily for me I do have access to itunes at work so it isn't all bad but very frustrating if I need to do something from home.

Question 2 - I have two email addresses with itunes & want to add some playlists from the other one to my iphone. Is this a possibility & if so how do I do it?

thanks in anticipation

Swanna