Sams Teach Yourself Microsoft Windows 2000 Professional in 10 Minutes

By Dorothy Burke and Jane Calabria

• Table of Contents
  • Copyright
  • Tell Us What You Think!
  • About the Authors
  • Introduction
  • Conventions Used in This Book
  • Lesson 1. Navigating Windows 2000 Professional
  • Lesson 2. Working with a Window
  • Lesson 3. Using Menus
  • Lesson 4. Using Windows 2000 Professional Help
  • Lesson 5. Using Dialog Boxes
  • Lesson 6. Working with Multiple Windows and Applications
  • Lesson 7. Copying, Moving, and Linking Between Windows and Applications
  • Lesson 8. Using My Computer
  • Lesson 9. Managing Files with My Computer
  • Lesson 10. Using WordPad
  • Lesson 11. Understanding File Properties and the Recycle Bin
  • Lesson 12. Printing
  • Lesson 13. Using My Network Places
  • Lesson 14. Using the Control Panel
  • Lesson 15. Using Outlook Express Mail
  • Lesson 16. Sharing Workstations and Setting Passwords
  • Lesson 17. Using Internet Explorer 5
  • Lesson 18. Web Site and Document Searching
  • Lesson 19. Troubleshooting, Restarting, and Disaster Planning
    • Task Manager
    • Restarting Windows 2000
    • What is a Computer Virus?
    • Curing and Preventing Computer Viruses
    • Creating a Startup Disk
    • Troubleshooting Windows 2000
  • Lesson 20. Customizing the Windows 2000 Environment

What is a Computer Virus?

A computer virus is an incomplete piece of programming that can do nothing on its own but, if attached to another program, can take over the other program and carry out its own mission instead of that of the host program. So, when you run the host program, it does something wholly unexpected and usually unwelcome. It may do something benign, like popping a message up on your screen. Or it may do something malicious, like deleting files or reformatting your hard disk.

Part of the programming built in to every virus is the ability to spread itself to other programs. When you run a program that is infected with a virus, the virus loads into your computer's memory and waits for opportunities to install copies of itself into other programs on your computer. Then, when you send a newly infected program to someone else, his programs become infected too. Because> programs reside everywhere in modern computers, in the boot record of every disk, in .com, .exe, and .dll files, and even in data files, you can pass computer viruses around with ease, and you must take extraordinary measures to avoid passing them around.

There are, in general, three kinds of viruses:

• Boot sector viruses: These infect the program that resides in the boot sector of every hard and floppy disk. They load themselves into your computer's memory when you boot up your computer (which is when the boot sector program runs). Your computer becomes infected when you receive an infected floppy disk, forget to remove it from your disk drive when you turn off your computer, then re-boot with it in the drive the next time you turn on your computer. This loads the virus into your computer's memory. From there, it infects your hard disk and every other floppy disk that you may put into the floppy disk drive.
• Program file viruses: These infect executable program files, such as .exe and .com files, and the library (.dll) and overlay (.ovl) files that the executables call into memory from time to time. Your computer becomes infected when you run the infected program. Then the virus infects other programs on your computer.

  Plain English

  Executable file The file used to start a program. Executable files can be identified by their icon, which typically matches the logo of the software product and has a file extension of .EXE.
• Macro viruses: These infect specific kinds of data files. For example, Microsoft Word data files (.doc and .dot files) can store programming in the form of Word macros. A Word macro can be programmed to act like a virus, in the sense that, when you run Word and load the data file containing the macro into memory, the macro writes a copy of itself into your Normal template. From there it can write itself into every other Word file that you load into memory. And, sooner or later, you will send one of those files to a co-worker. Macro viruses also infect Excel files.

The statistics on the number of new computer viruses being created every day are staggering—there are a lot of programmers out there with way too much time on their hands. Most viruses are a variant of another virus. While it's bad enough if your home computer gets infected (only you are inconvenienced), if a virus hits your computer at work, the ramifications can be much more far-reaching.

When a virus makes its way into an office computer, the chances of it "spreading" are good, as people in an office often share files. Just like spreading germs that make everyone get the flu, sharing infected disks spreads a virus through an entire company's computer system in very little time.

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