Your brother-in-law emailed you a file. You clicked on it and it won't open. What to do next? Well, the first thing to do, if you want to go about this systematically and learn something in the process, is to find out what kind of file it is. He may have sent you a photo, or an audio file, or a plain text file, or a Word document, maybe a spreadsheet, or god only knows what all. Usually, when you click on a file (or double-click it) it just opens up on its own. That's because your computer recognizes that particular kind of file and chooses the appropriate program for you. But in some instances the file type isn't recognized by your computer and so it does the digital equivalent of standing around scratching its head. Once you know what kind of file it is, then you can tell the computer what kind of program it needs to use to open it.
So, how to recognize file types? In most cases it's simple. You look at the file name, and the last bit, the part after the dot, will tell you. That bit is called the file extension:
.doc - Word files .txt - plain text files (Word opens these, but so can other text programs) .xls - Excel files .jpg - photo files .jpeg - also photo files .gif - different kind of photo file (may be animated) .mp3 - audio file .pdf - come on, you know this one, they're PDFs
So a file named " barbeque.doc" would be a Word file, while "barbeque.jpg" would be a photo, and so on.
Now the little list above shows just a fraction of all the file types that exist. For example, people with the newest versions of Word may be sending you files with the annoying .docx extension. You may have to download a little add-on thingy from Microsoft, but after that your regular copy of Word will open them. But the ones above are the most common.
I've found that the main reason that a file I've received in an email is unopenable, is that the person sending it accidentally removed the file extension while he was renaming it. So a photo file that was originally named "DSC00815.jpg" is now "Bermuda.sunburn". The problem with that is that "sunburn" is not a file extension. In order for your computer to recognize the file as a photo he should have renamed it "Bermuda.sunburn.jpg".
If you know he sent you a photo, and the file name doesn't look right, just rename it yourself, adding the .jpg to the end. That may just do the trick. You can't damage the file by renaming it, so even if you don't know what type it is you can try different extensions with no harm. You will get an error message when you change the extension, but it's safe to ignore it, and you can always change it back if you're wrong.
Most computers come pre-installed with some sort of software that will read the basic file types in the list above. You may not have Word, but you should have some sort of word-processing software that will open a .doc or a .txt file. Ditto for .jpg and .gif - you probably don't have Photoshop, but you most likely have a basic photo viewing or editing program. Spreadsheet files? Maybe not. If you don't have Excel you may not have a suitable program. Not to worry. You can always download a free program like OpenOffice or use a free web service like GoogleDocs. Audio files should not be a problem either. For PDFs you can download Adobe Reader or lots of other free PDF Readers.
So if you've taken a look at the file and it has one of the extensions above (watch out for any extra stray punctuation like a dot a the end that doesn't belong there), and you've opened those kinds of files above before with no problem, then there's something else wrong with the file and you may never know what the issue is.
You shouldn't be embarrassed to ask the sender what kind of file it is and to resend it. You'll be surprised how many times the problem turns out to be on their end and not on yours.