If you are using xp or ME, you can return to a restore point before you installed the files.
Nearly all windows recognized fonts go into the folder (directory) c:\windows\fonts
If the programs that installed the fonts is recognized by Windows, go to the control panel and uninstall the addition.
If that is not possible, then you will have to do it manually. It will probably be better if you have another system that is configured the same way as yours was, and copy the fonts folder to a disk or other media, and then add it to your corrupted system.
Do not delete anything until you know you have a replacement for the original files.
If you do not have another system, you can Identify the fonts you use on a regular basis and delete the rest.
Do this by going the fonts folder, selecting ALL, then while holding the "ctrl" key down, you unselect the ones you want to keep.
As a last resort, save your personal files and reload windows defaults from the disk after you have removed all the current fonts. Using this method will overwrite any preferrences you have made to your system. But it will restore the original fonts.