Helpful advice from Computer Hope http://www.computerhope.com/

A computer virus is a software program that has been intentionally created to cause a user grief, spread to other computers, or destroy data on an individual's computer. To help prevent a computer from becoming infected by a virus, software developers have developed antivirus programs that stay active on the computer helping to protect it. Note: Many computers do not come pre-loaded with an antivirus installed and computers that may include an antivirus often expire within 90 days.
The best method to check and protect a computer for computer viruses is to use an antivirus program. There are many different programs to choose from, but the better-rated brands are Kaspersky, Symantec, Trend Micro, and MSE. You can get just the basic antivirus program or a full antivirus suite, which often include other types of protection beyond just virus protection. You can also try using a free online virus scanner to check for viruses on your computer.
A virus or worm that is infected on your computer can cause this issue or another computer is using (spoofing) your e-mail address as the e-mail address of who is sending the virus or worm. When a network or user receives an e-mail infected with the virus that is capable of detecting the virus, it will automatically reply to your e-mail address.
Reading an e-mail message will not infect your computer with a virus or other malware. Computer viruses, trojans, and other malware infects your computer when an e-mail attachment is ran from an e-mail. If while reading an e-mail you double-click, run, or save any attachment and that attachment is infected with a virus your computer will then become infected. Even if you have no intentions of running or opening e-mail attachments, we still suggest that you use an antivirus protection program on your computer.
Yes. A firewall will not protect you from viruses and other malware. A firewall limits outside network access to a computer or local network by blocking or restricting ports. Firewalls help prevent your computer from communicating with other computers on the network and Internet.
Shutting down a computer allows the computer to close all open programs and exit the operating system, so nothing is running when the computer turns off. Below are the steps on how you can shut down your computer based off the operating system you are running on the computer. If you are not sure what operating system you are using see our steps on determining a computer operating system.
As you browse the Internet, everything you view is saved to the cache on your computer. Using cache helps everything load faster because data comes from your hard drive instead of a server in a different part of the world. To conserve hard drive space or keep your browsing private, you can clear or delete the history (cache). Select your Internet browser from the following list to get started.
Because most versions of Windows do not include a method of password protecting your files and folders, this page provides steps on encrypting files and folders instead. To password protect your files and folders in Windows, you need to use a third-party program. Tip: Before password protecting any document, you may want to create a backup of the non-password protected files and folder in case you forget the password in the future.
There are several ways to format a computer hard drive or solid-state drive to erase all of the information on a drive and prepare it to hold data. To proceed, select one of the methods from the list below and follow the instructions. Note: If you want to format a hard drive and reinstall Windows, see our page on how to erase a hard drive and start over.