Keep in mind that certain programs are associated with a certain type of file. For this reason, do not expect applications like Microsoft Outlook to open all attachments. If you cannot open an e-mail attachment from within the e-mail program, try saving the attachment to your computer's hard drive or a diskette. This will help allow your operating system (Windows) to open it.

Other common file extensions such as tif, jpg, bmp, cdr, dmx, fig and wpg are graphic files which are commonly mistaken as documents. A common mistake is made when users attempt to open these types of files in their word processor application such as Microsoft Word or WordPerfect and quickly learn that they are not documents, but merely objects that are designed for placement into a document. Error messages that occur related to "Unknown File Format", usually are caused by using the wrong program to open a specific document or attachment. It is very important to allow programs to save your files with their own extensions instead of creating your own. By doing this, your computer will know what application to open your file with in the future.