Computer viruses are small software programs that are designed to spread from one computer to another and to interfere with computer operation.

A virus might corrupt or delete data on your computer, use your e-mail and messaging programs to spread itself to other computers, or even erase everything on your hard disk.

Viruses are most easily spread by attachments in e-mail messages or instant messaging messages. That is why it is essential that you never open e-mail attachments unless you know who it's from and you are expecting it.

Viruses can be disguised as attachments of funny images, greeting cards, or audio and video files. Viruses also spread through downloads on the Internet. They can be hidden in illicit software or other files or programs you might download.
 

After you open and run an infected program or attachment on your computer, you might not realize that you've introduced a virus until you notice something isn't quite right.

Here are a few common signs that your computer might be infected:

• Your computer runs more slowly than normal
• Your computer stops responding or locks up often
• Your computer crashes and restarts every few minutes
• Your computer restarts on its own and then fails to run normally
• Applications on your computer don't work correctly
• Disks or disk drives are inaccessible
• You can't print correctly You see unusual error messages
• You see distorted menus and dialog boxes