Resolution is the reason your screen looks 'big' and you can't reach the "OK" button.
Close any programs you have open and right click on an empty space on your Desktop, then select Screen Resolution (Windows 7) or Personalize (Windows Vista) or Properties - Settings Tab (Windows XP)
When you see a menu/option containing resolution measurments - ie: 800x600, 1024x768 - you are in the right place.
Choose the largest one available. Typically on a Laptop / Notebook this will be what is called the "Native Resolution" - or, the best size that suits your screen dimensions.
Now you have access to the "OK" buttons etc for everything else. However, if this does NOT do as I have described, the issue may be with your video card, or the drivers (software that runs it).
The error message you are getting about MIME is a bit more puzzling. You do not need to download MIME, you can't. It is not something that is 'missing' from your compuer. Think of it more as an industry standard, a method that all computer programmers agree upon.
As explained in the link below, MIME types are basically 'common' types of files, or the "expected" contents of a file according to the extension. You may have seen file extensions; like a JPEG file. As a human, you know that a JPEG file is an Image. A computer is not an "Intelligent Being", it doesn't actually "know" anything. It is instructed that a JPEG file is an Image file. So when it is expecting a certain type of content in a file, but it is given another, it will not be able to process the file according to the instructions.
http://www.boutell.com/newfaq/definitions/mimetype.html
Basically, your browser can not process the file you are asking it to open. Something may be disrupting the file transfer and causing the file to be incomplete. A bad internet connection, or hard drive issues. If you are downloading the file, you should try saving it to a location on your hard drive before running it. Perhaps your computer is having trouble caching the file if you are trying to run it. Save it first, then select Run.
Back to your Home Page. Just go to the page you want by typing the address in the address bar, then click the little downward arrow NEXT to the Home button on the IE toolbar (IE7 or 8). This has an option to Add or Change your home page. Use the Add as only home page option if you just want one page to be your home page.