missing system fonts?!?

ok, we have a website here at work, and one of the buttons doesnt show up right anymore :EDIT on one machine /edit. In the source, it says the font for the button is: "FONT-FAMILY: serif". I can change that to Verdana, and it shows up fine. I've googled Serif, but there are 100's of diff kinds of this font. I'm not even sure which serif it's trying to use by default? How can i restore system fonts on a winnt box? Other windows versions have System File Checker, but i dont think WINNT does, any ideas? :confused:

You can just copy the font from your installation cd or some MS-word cd or something, maybe you can dowload it from the internet, ... just guessing

my problem is, there is no 'serif' font, theres serifo and serife and all sorts of others, but the source just says serif, so i dunno exactly which font it's trying to call. All i know is it's a system font. If some one can tell me what font "FONT-FAMILY: serif" would call on, that would help, otherwise a way to delete and restore/reinstall all of my default system fonts would be helpfull.