Remove all the Antivirus programs currently on your computer
Install Avast Antivirus, telling it to run a boot time scan during the process
Run the Boot Time scan, removing all found viruses
Learn what to do when a future real time scan discovers a virus
But I already have Antivirus!
Even if your computer came with Antivirus or you downloaded another antivirus, it may have been a trial version, it also may have become deactivated somehow along the way. Because of this, unless you are absolutely sure your antivirus is up to date with the latest version and virus definitions, and actively running, I highly recommend uninstalling it and going with Avast.
Remove All Other Antivirus
First off, Antivirus Programs don't play nice together, so it is critical that you uninstall any antivirus you currently have on your computer.
To do this, go to the start menu, then click "Control Panel" (sometimes under settings). Click "Add/Remove programs". Scroll down the list of programs installed and look for anything that says Norton, Symantec, McAffee, AVG, or anything else about Antivirus. Remove all of them. You may have to reboot after uninstalling each one. Tell them not to reboot until you have removed all of them to save you from having to reboot multiple times. Once they are all removed, reboot your computer.
Click the above link and then click the download box next to the english version. Click "Open" or "Run" when you are given the option. Once the program downloads, walk through the installation. One page will ask you if you want to run a boot time scan on your next startup, Click Yes to this option and accept all default settings for any other screen.
Reboot your computer, and it will run a boot time scan, DO NOT CANCEL the scan when it runs. This may take a while.
Setting avast to run program updates automatically
Avast is great because it automatically checks for and downloads new virus definitions every 4 hours by default. It also checks for updates to the actual antivirus program, but asks you each time it finds an update. To set it to automatically install the updates, right click the blue circle with the a in it in your system tray, and click "program settings". Under "Update (basic)" change BOTH of the options to Automatic, and click "Ok".
IMPORTANT! Although Avast is free, you need to Register it or it will disable itself after a short time. The registration lasts a year, at which time you will need to re-register it.
To Register Avast, once your computer starts up again right click the blue circle with the A in it. The second option down on the menu will say "Start avast! Antivirus", Click it.
A small box will pop up with a blue link that says something about registration. Click that link and a web browser will pop up with a registration form. I believe you only really need to fill out your name and your Email Address. Once you do and click next, you will be emailed a registration code. Check your email and get the code (Select it and copy it (right click->copy)). Go back to the antivirus and paste the unlock code into the registration box and click ok.
Congratulations, you are now protected from viruses. Remember in a year when it says to register that you really need to do it. Way too many of the home computers out there have antivirus installed but it is out of date or not registered properly, therefore completely useless.
Is It Running?
You can tell that Avast is running properly by the blue sphere icon with an A on it that shows in the bottom right of your computer. It should spin around every so often (indicating that it is scanning something). If this ever goes away, something is wrong and you should make sure it is still running properly.
What do I do if it ever finds a virus?
If you do find a virus any time in the future, come back to this site and follow the instructions for the "Boot Time Scan" on the Antivirus Refresher Page. If you just installed Avast, and the boot time scan came up clean, you can scroll down and move on to the next page, but remember to come back if a virus ever is detected in the future.
Progress Tracker Update (Click the checkbox and click next to update the progress checklist)
I have installed Avast! Antivirus, recieved a free registration code via email, and entered the registration key into the Avast! Program.
LEGAL DISCLAIMER: Although these instructions have been tested on thousands of computers without incident, and chances of any damage or loss of important data resulting from following these instructions are virtually zero, there always exists a very small chance that something could go wrong. I add the following warning not because I ever believe that anything will happen but because today's lawsuit happy world requires it:
Although I will attempt to assist you (via the contact me form) with issues that arise from following these instructions, you are using this website at your own risk, and I am not legally responsible for any damage or loss of data that may occur related to the use of this website.