NWA-PCUG Newsletter Article
Windows CAB Files
by Dale Oliver, Vice President, October 2000
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It appears that the Q&A sessions have been received with enthusiasm by the club members. Kudos to Bill Shook for the great idea! The board members will discuss having a Q&A session in place of a scheduled topic at least once every quarter. Please give us your feedback regarding this idea -- we'd like to hear what you think.

I picked up some hints from the September Q&A session that helped me solve an annoying little Windows glitch that I had been living with for awhile. These sessions are very informative and cover a wide variety of subjects, so I encourage everyone to show up for these meetings and actively participate in both asking and answering questions. We have an impressive amount of member knowledge at every meeting, and it's really gratifying to see members helping each other in such a selfless manner.

One of the questions that came up during the September Q&A session that was not covered in particular depth--but is quite helpful to know about--is Windows CAB files. I'll discuss the basics of what they are and how they are used in this column.

Think of CAB files as digital storage cabinets. Just like a typical archive file, CAB files contain other files in a compressed state. Unlike ZIP, ARC, LZH, TAR or other more generic compression formats, CAB files are a Microsoft invention that are generally used for storage of Microsoft-specific products.

CAB files are a clever way to place the contents of Windows installation disks onto your hard drive for easy access. In Windows 98, the files are typically stored in the \Windows\Options\Cabs\ folder, where they are named WIN98_XX.CAB (the XX is replaced by a two-digit number uniquely identifying the particular cabinet file). These CAB files prevent you from having to dig around for your Windows installation disk every time you want to change or add Windows features, install new hardware, etc. Instead, Windows looks into this directory and uses the CAB files located there. If the needed file is not available on your hard drive, you will be prompted to insert the Windows installation CD.

As you might expect, this convenience doesn't come without a price. Expect somewhere around 100 MB of disk space to be used for storing your Windows CAB files. While this used to seem like a fairly large amount of disk space, it is relatively insignificant with the large new hard drives that come standard on computers today. A good tradeoff, in my opinion.

Another, possibly lesser known use of CAB files, but a very important one nevertheless, is the fact that they are used to backup your Windows registry files. By default, these backup files are stored in the \Windows\Sysbckup\ folder. Windows keeps five separate copies of your registry here, using the file names RB001.CAB through RB005.CAB. More advanced users can modify the ScanReg.INI file located in the \Windows\ folder to configure a number of specific features relating to registry backups, including the number of backup registry copies to keep.

You will likely see a number of different CAB files in the \Windows\Options\Cabs\ folder, including some used for storing drivers and various other things, including CAB files from third party software vendors. If you are curious about the contents of a particular CAB file, you can use Windows Explorer or My Computer to view them. Simply browse the \Windows\Options\Cabs\ folder and double-click on whichever CAB file you're interested in. Windows will automatically run the CabView program to allow you to view the contents of the selected CAB file. If you have WinZip installed, the WinZip program will display the file contents instead of Windows' CabView.

If would like to learn more about CAB files, you can find an enormous amount of information on the Internet as well as computer-related books.

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