How to Identify Computer Virus Symptoms

Instructions

Look for obvious changes.
Look to see if there are any changes to your desktop, your favorites or in the way your computer acts in general. If your desktop icons have moved around or if anything has been added to your desktop, this is a sign you have a virus. Look in the "Add/Remove Programs" section in Control Panel and see if there are any programs that you don't remember installing. Often a virus will install other programs that will cause problems. If you have a new toolbar in your web browser, this is another sign that you may have a virus.

Disconnect from the internet.
If your computer acts differently when you are connected to the Internet, that is another sign you have a virus. One of the chief purposes of many viruses is to steal your computer resources. When you're not online, someone on the other end isn't able to get to your resources.

Check your speed.

One of the key ways to know if you have a virus is if your computer is running slower. Sometimes the computer will run just a little bit slower, but after having a virus for some time the computer will become extremely slow in everything it does. Disconnecting from the Internet may speed your computer up, but with malicious viruses it may not matter whether or not you are connected to the Internet--the virus will use your resources just to cause you problems.

Beware of errors.

If you are getting strange errors or just more errors that do things like close your programs or cause you to restart your computer, there's a good chance you have a virus. Sometimes errors are normal, but they shouldn't happen constantly. Keep a log of when you get errors, what you were doing when it happened and how bad the error was.

Listen for noise.

If your computer is making a lot of crunching noises accessing the hard drive when you aren't doing anything, then it's likely being controlled by a virus or someone who set up the virus. Most of the time when you're not using your computer it shouldn't be doing anything.

Inspect your security software.

Check to see if your virus software, firewall or Windows updates have been changed or disabled. If you have security but it's not up-to-date or not quite good enough, a virus will disable the software to give itself and other viruses more access.