Content-type Always text/html

I'm running IIS 6.0. I was able to download MS EXCEL spreadsheets
(application/vnd.ms-excel) and PDF Files (application/vnd.pdf) until the web
server crashed. For some reason the spreadsheet and PDF responses have the
context-type text/html.

Is there an IIS 6.0 mime type setting or registry setting that may be
corrupted?

It appears that all reponses have the context-type text/html.

Your help is appreciated.

Thanks,
Mark