Before you do that you mention pictures. Is this all attachments that open up in notepad or certain types? Or perhaps your really only get pictures in email?
It may be a simple file association that needs to be changed. What is the extension of the files that you are trying to open in Outlook? Do you have any pictures with the same extension (.jpg, .bmp, .tif, etc.) saved on your hard drive? What do they want to open with?
If they want to open with notepad you can right click on the file choose "open with"->choose programs and select "always use to this program to open with file type". The exact process just mentioned varies slightly from operating system to operating system but if you can verify whether it may be just a matter of a file type problem or not we could be more step by step on how to change depending on your operating system.