What file formats? What version of Windows?
The more specifics you can give us about your configuration and the problem you're having, the faster we'll be able to help.

under folder options, in the "file types" tab, we already have the .tiff file extiension and need to add .tif. i don't care whether it's there or not but we have users that just don't understand they can right click on the file and rename it to .tiff so it would be easier if i just added that file extiension as an option. Windows 2000 terminal server. thanks.