The application 7-Zip has been installed on all ITS-provided computers to augment Windows XP's built-in support for compressed files.

While XP can deal adequately with archive files in the .zip format, 7-Zip can open .001, .7z, .arj, .bz2, .cab, .cpio, .deb, .gz, .iso, .lzh, .rar, .rpm, .tar, .z, and .zip files. Additionally, 7-Zip can create archive files in the .zip, .7z, and .tar formats.

When dealing with .zip or other archive files, there are three basic operations:

1. Opening an existing file — "unzipping" an archive to reveal the individual files within. When the zipped file is closed the archive remains intact and the individual files are no longer visible.

2. Extracting an existing file — "unzipping" an archive to make copies of the individual files within. When an archive is extracted, the original .zip file remains intact and copies of its individual files remain on the computer (usually in a folder with the same name as the original .zip file but minus the .zip extension).

3. Creating an archive file — "zipping" individual files into a single archive file.

Opening an archive file

Any file with a .zip extension can be opened by Windows.  The file's icon will look like a folder with a zipper. Double-clicking the icon will open the .zip file just like a folder opens — the files within the zip file will be visible and accessible just as files within a regular folder are visible and accessible. When the zip file is closed however, you will see just the zip file and not its individual files.

Extracting an existing archive using Windows' built-in functionality

If you want to extract the contents of a .zip file (to make permanent copies of the archive's individual files) using Windows:

1. Right click it, and select "Extract All…". This will launch the Windows Extraction Wizard.
2. Click Next, select a destination directory for the extracted files, then click next again.
3. Click Finish to close the Extraction Wizard. If you leave "Show extracted files" checked the folder with the extracted files will open.

Extracting an archive using 7-Zip

7-Zip's file extraction method avoids the Windows Extraction Wizard. Simply right-click the .zip file as before, select 7-Zip, then select "Extract Here". This will extract the contents of the archive into the same location as the original .zip file.

Note: be careful with this feature — it's easy to lose track of the extracted files if they mingle with other unrelated files, and extracted files can easily clutter things up. For example, if your archive file is located on your desktop, "Extract Here" will copy all of the files in the archive to your desktop. This may be what you want if the archive contains just a file or two, but is probably not what you want if the archive contains hundreds of files.

An alternative to "Extract Here" is "Extract files…". This feature of 7-Zip allows you to choose a location into which the files will be extracted.

Creating archive files

To assemble individual files into a zipped archive:

1. Open My Computer and browse to the file(s) that you want to put in your zip file.
2. Select all the files that you want included, then right click one, and select "Add to archive…".
   
3. This will bring up the "Add to Archive" window. Be sure that the Archive format is set to Zip, and give your new .zip file a name. Here it is shown as example.zip.
   
4. Click the ellipsis button (three dots)  in the upper right to browse to the folder in which you want to create the archive.  (By default, 7-Zip will create the archive in the same location as the original files.) Once you have named your new archive, click OK to create it in the location you specified.

This same method can be used to add files to an already-existing archive:

1. Browse to the file you want to add and select it.
2. Right click and select "Add to archive…".
3. Rather than specifying a new name, choose an existing archive from the "Archive:" drop-down.

This feature of 7-Zip makes it easy to create an archive from files in different locations and/or create an archive incrementally.