OS X only permits changing the font size but not the font itself. There are third-party interface modifiers that may enable you to make more extensive changes, but since the basic system fonts are embedded they are not easily changed. The freeware tool, TinkerTool, can be used to make some font changes, but icon fonts. Look for it and other software at VersionTracker or MacUpdate.
Are you referring to the size or typeface of the font? Font size in iTunes is controlled in the General section o iTunes preferences. The size of icon fonts is set by clicking on the Desktop and selecting Show View Options from the Finder's View menu.
I'm not sure how that happened. A lot of users would love to know how to change the Desktop icons' font. Are you sure you child didn't delete fonts from the /Library/Fonts/ folder?
No because I see the factory default font everywhere else. Another thing that happened was that she changed the screen resolution to 1064x768 stretched, which I changed back to 1680x1050. That was the first thing I did which did not change the font back to the original. BTW thanks for trying to help. Any other suggestions?
Hmmm, could she has accidently change the System Language of the mac besides English, so the apps etc are displaying the fonts other than the "standard" U.S. Eng font?
System preferences > Appearance > Turn off text smoothing for font sizes xx and smaller
This was the changed parameter. It was changed to font size 12 and smaller. Therefore all desktop fonts, itunes fonts, finder, etc. were not smoothed out and took the appearance of times font.
Thank you to everyone who tried to help. We have now all learned something.