There is a setting in Windows 8 in the Modern interface which you may have turned on: I know that the directions are for making things larger, but it also applies to making things smaller than your current resolution. Anyhow go in and check it out and see if helps or not. This setting is only available in the Modern Interface, and not by right-clicking on your desktop or icon.
Make text and other items on the desktop larger
If text and other items (like icons) on the desktop are too small, you can make them larger without changing the screen resolution.
1.
Open Screen Resolution by swiping in from the right edge of the screen, tapping Search (or if you're using a mouse, pointing to the upper-right corner of the screen, moving the mouse pointer down, and then clicking Search), entering Make text larger in the search box, and then tapping or clicking Make text and other items larger or smaller.
2.
Drag the slider until the items in the preview image are the size you want them to be.
3.
Tap or click Apply.
You'll see the change the next time you sign in to Windows.
http://windows.microsoft.com/en-us/windows-8/get-best-display-monitor