Windows XP, Vista, and 7 include a free utility that can unpack compressed files and display them in their original formats. WinXP/Vista/7 users can right-click the file and select Extract All. The utility lets you choose where to place the extracted file and whether to open the folder and display its contents when the operation completes. If you are running an older version of Windows (Win2000 or earlier), you’ll need a separate utility.


EXPAND YOUR HORIZONS

If a compressed file has a file extension other than .ZIP, it will require a specialized compression utility to unpack it. Most compression/decompression software can extract the original files from a dozen or more compressed formats. One such program that has been around for quite some time is WinZip ($29.95 for the Standard edition, $49.95 for WinZip Pro; www.winzip.com). We also like WinRAR ($29; www.rarsoft.com), especially if you also plan to compress files and send them out. (Both give free trials, so you can compare before you buy.) However, if you only need to unpack files, a free utility might suit your needs just as well. For example, IZArc (www.izarc.org) opens more than four dozen archive types (more than many fee-based compression utilities), and you can configure it to run your virus scanner as you start unpacking the archive. ZipGenius (www.zipgenius.com) is another option, and it supports more than 20 file types.


OFFER AN EXTENSION

Some OSes (notably Apple’s OS) store the file-type information as a header inside the file and don’t require a file extension. Mac users sometimes use file extensions to make life easier for their Windows-loving friends, but it isn’t necessary. If a file unpacks and has no file extension and you know what type of file it is, you can simply add the extension to the end of the filename. Turn Officemeeting into Officemeeting.jpg, and you will be good to go, assuming it is actually a JPG file. This plan will fail miserably if you provide the wrong extension, leaving you to query the sender. However, if you at least know the file type (video, digital photo, and so on), and there are a reasonable number of options, a little experimentation may take you a long way. For example, if you know Johnsbirthday is a digital photo file, try .JPG, .TIF, .EPS, and maybe even .GIF or .PNG file extensions. You should get there eventually.


COMPRESSED OR NOT?

If you can’t find a program to decompress a file, and you are not certain it is an archive, then it might not be. There are many more file extensions than most of us will ever encounter. Many of these represent files from proprietary programs not in common use. For example, the information needed to portray data spatially through a GIS (Geographic Information Systems) program often comes divided among a half-dozen or so files; these are usually zipped into a single archive for ease of transport (and because they are pretty useless alone). If you accidentally obtain one by itself, say an SHP (shapefile, which describes geometric forms) file, you won’t be able to do a darned thing with it unless you have its partner files (usually at least SHX [spatial index] and DBF [database] files). Fortunately, a quick search on Google will at least tell you what you have.

SOFTWARE LOCKDOWN

Are you on a corporate laptop or public computer where you cannot install software? Don’t worry. You can install a compression utility on a USB drive and access it simply by inserting the drive into an open USB slot on any PC. IZArc2Go (free) is USB-based. Best of all, for people working from a public computer, the utility leaves behind no trace of your activities when you decide to move on.

CAN’T TOUCH THAT

Compressed archives originate from many programs and OSes. Consequently, just because you can unpack a compressed program doesn’t mean your PC can open it. If you double-click an unpacked file that has a three-letter file extension and Windows doesn’t associate it with a particular program, Windows will ask if you want to look for a program online or tell it which program to use. With some file types, Windows does a decent job of determining what program created the file. It may actually lead you somewhere useful. If not, try searching Google for the file extension to see what pops up. If you can determine the file type (video, graphic, or document, for example), you may be able to convert the file to another similar but usable format. Zamzar (www.zamzar.com) supports an array of file types, and it is free. (But you should expect ads and pop-ups.) Media Convert (media-convert.com), although ad-supported, is free, as well.

KEEP IT SMALL

When size limitations or bandwidth restrictions affect your ability to send large files, a compression utility can be your best friend. There are many available, but beware that most compression tools can create far fewer archive types than they can unpack. Some tools, including WinZip and WinRAR, can divide extra-large files and folders among multiple archives when you compress them. In some instances this is ideal for moving a group of large files through without having to compress each one individually.

The most universally compatible option for sending compressed files when you are uncertain of the recipient’s capacity is a SEA (self-extracting archive). SEAs don’t require the recipient to have any other program on his machine because they contain applets that perform the unpacking internally. Some SEAs have the .EXE (executable) file extension. Many virus programs flag EXE files as troublemakers, and some companies and public locations won’t let computer users download those files. If you send out an EXE file, make sure you alert the recipient that it is safe to open.