When attaching a file to a message, it opens a dialog which lets you browse for files. When I click on “All Files (*.*)”, it allows you to choose various file types such as Word Documents, Word 97-2003, Rich Text Format, Text Files, etc...
Is it also possible to add my own file types here such as Excel, PowerPoint and Adobe PDF-files?
No, you cannot directly modify this dialog. It is actually the default Word "Open File" dialog which is why you see only Word related file types.
However, you can type
You can also search for multiple file types at once by separating the file type with a semi-colon. For instance, to show only Excel and PDF files, type;
To reset the filter, simply type
*.* and press ENTER.
You can quickly apply your own file type filter when attaching or opening a file.
Bonus tip 1
You can actually also use this trick if you know part of the file name. For instance, when you know that the word “report” is part of the file name, type
*report* and press ENTER to list only the files in that folder with the word report in their name.
Bonus tip 2
You can also use the Search field in the top right corner of the dialog to apply a filter or do a search (not available on Windows XP). This will include all sub folders as well.