Windows and IE Suddenly Display Large Fonts.

I have Windows XP, Media Center Edition (Version 5.1 9Build 2600.xpsp_sp
2_gdr.070227-2254: service pack 2) and Internet Explorer 7. Overnight, the
display has changed. Fonts now look different, and much larger than before.
This is true to some extent on the desktop and to a large extent on Internet
Explorer.

We haven't done anything to change our settings. This just seems to have
come from nowhere.

Here's what I've tried so far:

Here's what I've checked so far:

* On Internet Explorer, when I go to the "Tools" menu, then to
"Internet Options" and then "Accessibility", all the boxes are unchecked
(as they should be).
* On Internet Explorer, when I go to the "View" menu, then to
"Text Size", the setting still indicates "Medium" (as it always has in the
past).
* On the desktop, if you go to "My Computer", then to "Control
Panel", then to "Appearance and Themes", and then "Change the Screen
Resolution", that setting seems to be fairly low, as it always was in the
past.

This problem seems bizarre and very frustrating. I would appreciate any
help you can provide.