If that problem is only with Firefox, see this: <br /> https://support.mozilla.com/en-US/kb/Page+Zoom If it affects all your programs and the desktop, did you reset the screen resolution? <br /> http://en.wikipedia.org/wiki/Screen_resolution

Did you make changes to the Windows DPI setting? *http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/display_use_large_or_small_fonts.mspx?mfr=true Try to disable some settings in the Properties > Compatibility tab of the Firefox desktop shortcut. * disable display scaling on high DPI settings ---- Decrease the String pref layout.css.devPixelsPerPx from 1.0 to 0.1 in 0.1 or 0.05 steps to adjust the size of all fonts and other elements in Firefox. The layout.css.devPixelsPerPx pref is a String value parsed to a float and allows to fine tune the dimensions of all elements (user interface and web pages) more precisely (resolution 0.1 or 0.05). You can use values between 0.05 and 1.0 to reduce elements in size or use values greater than 1.0 to magnify and make elements larger (percentage divided by DPI, % / DPI). *http://kb.mozillazine.org/about:config