Reinstalling fonts

I am running Office XP on a Windows 2000 workstation. I seem to have lost my Times New Roman font (times.ttf) as well as an number of other common fonts. When I try to reinstall, I get a message that says the font already exists, delete and try again. I deleted all instances of times.ttf, but continue to get the error when trying to reinstall. Any ideas on recovering lost or damaged fonts would be greatly appreciated.