Generally you will want to open the attachment with a program. First find out which program to open the attachment with, for instance, if the file has an extension of .doc then the file is probably a document so you can try opening it with MS Word. If the file ends with a .zip, then it is compressed and you will need to decompress it first. You can do this with WinZip. If the file ends with .hqx or .bin or .sit, then the file is compressed/encoded for a Macintosh, and you will need Stuffit Expander in order to decompress/unencode the file.