I messed up Gnome desktop themes

["Vicente Barreiro" <vmbarreiro@earthlink.net>]

I'm trying to reset my font size to the original size (current size is too
big), but when I get to Gnome's control Center and select desktop/theme
selector, the theme capplet doesn't show. There is no options to select
anothe theme let alone to change font size.
Are there some files/directories that can delete to bring everything to the
original default configuration?

Thanks,

Vicente.