1.  Maybe you really don’t want to!  While the email messages themselves are rarely dangerous, attachments are where viruses often lurk.  Files with the extension .exe (see below for an explanation of “extension”) are so potentially dangerous that many email systems won’t even allow them to be transmitted as attachments.  You should never open any attachment without a quick moment of suspicion - were you expecting this message, and is it from a trusted source?

2.  People are often thoughtless about sending attachments.  If it contains nothing but plain text, they should have copy-and-pasted it right into the body of the message, and avoided the attachment in the first place.  If they are sending photos, which are often huge files, they should have posted them to a website for viewing.  (See our recent column about Picasa Web.) If they are sending you another corny movie or PowerPoint show with cute kittens, they should have realized that 16 of your friends have already sent you that one.

3.  Perhaps you don’t have on your computer the program that created that attachment and so you have no way of opening it.  If your friend sends you a movie in Quicktime format, for example, and you don’t have Quicktime on your computer, you may not be able to play it.  If the secretary of your club writes in WordPerfect and your word processor is Microsoft Word, then you might not be able to open the file at all, or even if you can, its formatting may be wonky.  (Wonky is just a high-tech term for “Doesn’t look right.”)

4.  It gets worse!  Even though you appear to have the program you need to open the file, it’s possible that you have an incompatible version, perhaps simply because it is older. Microsoft, in its wisdom, has just made a huge contribution to this messy situation.  A Microsoft Word document filename is usually something like    report.doc     a PowerPoint show is a  show.ppt   and a spreadsheet is   budget.xls     (The digits after the .  are called the extension of that file.)  Sometimes recently you will see that the extension has added an x at the end, such as  .docx  .pptx   .xlsx  or whatever.   This indicates that it is a file created with a version of Microsoft Office that is 2007 or newer.  People who create such files would be better advised to save them in the older format, which is easy to do, for the sake of the vast majority of people like yourself, for whom it is inconvenient to try to open the newer ones.  But they seldom do.  Your solution is to download and install the Compatibility Pack that Microsoft now offers as a limited workaround for people with Microsoft Office 1997, 2000, XP and 2003, and allow them to open those newer format files.  This does NOT give you a new version of Office, but just modifies the older version you already have.

Off on a tangent, I might also mention that the 2007 and newer versions of Microsoft Office (2007, 2010, 2011) are VERY different from their predecessors in many other ways too, and that there is often a lot of discomfort for people in learning the new ones.

5.  Sometimes it’s a bit confusing that an attachment behaves differently on one computer than another.  That could be because that file type might be associated with a different program on the second computer.  Music, photo and movie files can be displayed by many different competing programs, and photos that display on one computer in Photoshop, for example, might show up in Irfanview or your camera software on another.  Sometimes new programs change your file association automatically when they are installing, and you have to change it back again if you don’t like the new look.