Microsoft Corp.’s Internet Explorer and other browsers such as Firefox are the main tools for navigating the Web, but there are numerous accessories, called plug-ins, that enable you to do more. This software, and a treasure trove of other computer programs, are available on the Internet (as are Internet Explorer and Firefox).

Some of this software, including Internet Explorer and Firefox, is "freeware," i.e., free. Some is shareware or commercial software offered on a free-trial basis. You download it and try it out. If you decide you want to keep it, you register it and pay the price. Some shareware is based on the honor system. Other programs are configured so that, if you don’t pay for it, it stops working after a set time or number of uses.

The following plug-ins should be in every surfer’s tool box.

Adobe Acrobat Reader: Adobe Acrobat is a program that enables people using computers based on different operating systems, such as Microsoft Windows or the Macintosh OS, to convert their files into a form readable by all computers, so long as those machines are using the free Adobe Acrobat Reader software. Adobe makes its money from Adobe Acrobat, the software used to convert the files into ".pdf" (for "portable document format") files. Many Web sites, including government and corporation sites, offer documents in ".pdf" form. You need Acrobat Reader to view them and print them out.

You can find Acrobat Reader at Adobe’s Web site: http://www.adobe.com. Many sites that offer documents in ".pdf" form also feature a link to Adobe’s site, making it easy to get the software when you need it.

RealOne Player: RealNetworks’ software allows you to hear audio and view video sent over the Internet, including a radio news story you may have missed when it was first played, a replayable recording of a statement at a news conference or music from an "Internet broadcast station" that uses the Net instead of the airwaves to transmit its programming. 

You can find the free software at http://www.real.com. If you are willing to pay a one-time fee of $19.99, you can also obtain an enhanced version of the software called RealPlayer Plus, which adds better video and other features, according to the company. I've found the free version equal to my needs.

The RealNetworks site includes a guide to RealPlayer programming, including news, on the Internet: http://www.real.com/guide.

Video requires a relatively speedy Internet connection for the best results. However, even if the link is a powerful T1 or T3, Internet congestion or heavy traffic at a given site can make audio or video choppy or even inaccessible.

Windows Media Player: Microsoft’s entry, which uses its own format.. Find it at http://www.microsoft.com/windows/mediaplayer/default.asp.

Microsoft also has a guide to Internet audio and video: WindowsMedia.com at http://www.windowsmedia.com.

Quicktime Player: Apple Computer’s free program enables you to play movies on your computer, either downloaded from a Web site or while online. You can find it at http://www.apple.com/quicktime/index.html.

Shockwave and Flash: Macromedia’s Shockwave Player and Flash Player add interactivity, including interactive maps and animation, to Web sites. The free "viewers" can be found at http://www.macromedia.com.

Winzip: Not a plug-in, but one of the most useful shareware programs. Winzip compresses software and data, saving space on your hard drive or allowing you to put large data files or programs onto a few floppy disks. The newest version also encodes binary files such as sound, video and picture files into text, making them easier to send over the Internet.

You can find Winzip at http://www.winzip.com.

There are scores of other plug-ins and useful auxiliary programs.  In most cases, if a plug-in is needed to view certain content -- such as a "virtual tour" of a room or crime scene -- a link to the plug-in will be provided (or should be).

Other software can be found at Shareware.com (http://www.shareware.com), a nice site maintained by the CNet computer news service.

Another great site is TUCOWS (The Ultimate Collection of Winsock Software), which features a rich, categorized selection of software. TUCOWS has duplicate, or mirror, sites scattered around the world. Enter the main site (http:// www.tucows.com), then look for the one closest to you when downloading a program..

If those don’t do the trick, try Jumbo (http://www.jumbo.com).

Good luck, but remember to check EVERYTHING you download, no matter how good the source, for viruses. Up-to-date antiviral software will serve you well.