MIME (Multipurpose Internet Mail Extensions) types are used to instruct a Web browser or mail application how to handle a file received from a server. For example, when your Web browser requested an item on this server, it also requested the MIME type of the object.
Some MIME types, JPEG’s for example, can be displayed inside the browser. Others, such as Word or Excel documents or EXE files, require an external helper application to be displayed or downloaded. You may have tried to make some files downloadable from your web server only to get an error when trying to view or download the file.
HTTP Error 404 – File or directory not found.
You know the file is there and the link is correct, but what you missed was defining the MIME type on the server. There are two ways you can remedy this, you can add a wildcard MIME type “*” which would allow all files to be downloaded or viewed, or you can do it the secure way and add MIME types only for those files you wish to allow. Important Be sure you backup the IIS metabase before you change any of these settings.
First, open the IIS MMC from Control Panel | Administrative Tools. Right click the computer name and open up Properties. Click on MIME Types and then click New. Enter the file extension (.exe for example) and then type “application/octet-stream” in the MIME Type dialog box.
Click Apply and your IIS server will now server these files. If you wanted to serve all files type * in the extension field.