Viruses come in all shapes and sizes. One might give you annoying popup ads, while another might silently steal your data. Knowing you have a virus isn't always easy, which is why I've given you 5 signs to watch for.
Once you know you have a virus, removing it usually isn't too hard. You can see all the steps here.
Unfortunately, some viruses just don't want to give up. They might even lock you out of your computer completely! How can you possibly fix it?
If your computer won't even start up thanks to a nasty virus, you should try using AVG's Rescue CD. AVG anti-virus is one of my recommended free anti-virus utilities. The Rescue CD is AVG's prescription for really bad infections.
It's a set of tools that doesn't require your operating system to run. It can boot from a CD or USB flash drive and unpack itself to clean your computer of viruses without having to reformat your drive.
When you click the blue "Free Download" button, you'll have 3 options. The first is an ISO file meant to be burned to a CD. The other two options are RAR and ZIP respectively. These should be installed on a USB flash drive.
To use the CD/ISO version, you'll need to burn the image file to a disc using a program like CDBurner XP. That's because your standard Windows disc burning utility won't be able to do it properly.
To use AVG Rescue CD on a flash drive, download the RAR or ZIP file and extract the files to your hard drive. A program like 7-Zip can open the RAR or ZIP file if you don't already have a program that handles it.
In the unzipped directory, find the Setup program. This launches a wizard will guide you through the process.
WARNING: Do not run the "makeboot.bat" file from your hard drive! This will basically make your computer unbootable. Follow the setup wizard's instructions exactly!
It's a very good idea to set up a Rescue CD now before a virus gets on your computer. If you don't, you'll have to use a different computer for all this.
Once your CD or flash drive is prepared, insert it into your computer and start it up. You'll need to set your computer to boot from the CD or flash drive. Different computers have different ways of doing this.
For example, many computers have you press F8 or F11 during startup to enter the boot menu. From here you can select your CD drive or a removable drive.
You might need to press ESC, DEL, or F2 during startup to enter the BIOS and change the Boot Options. Check your manual or contact your computer's tech support if you can't find the proper method for your computer.
Once you've booted from the Rescue CD, scan for viruses and delete or rename the results. Be careful when choosing to delete, because certain files may be crucial to running your computer.
Also, depending on how recently you created your Rescue CD, you may need to Update AVG. You can find very detailed instructions on how to use AVG Rescue CD here.