Removal of Windows Service Pack 3 has messed up my Screen DPI?

I removed the service pack 3 from my computer because the installation of the pack made it impossible for me to print architectural drawings from my design program. Having removed the pack, I was able to print, but my screen DPI (dots per inch) is now huge. My screen looks like a bad comic book and I can’t seem to fix it in my control panel. I have reinstalled the service pack 3 and all the other available updates, yet nothing changes. How do I get my screen back?