As a general rule, paid antivirus programs that constantly update and monitor your system offer a greater level of protection than their free equivalents. However, free utilities can still help restore infected computers.
The following utilities can be used when a virus has not entirely incapacitated an infected computer:
You can also use the following free antiviruses:
Free antiviruses are often cutdown versions of paid programs. However, it is still better to use a free version than none at all.
In addition, the majority of antivirus programs offer free trial versions which can be used to scan and remove viruses from an infected computer.
If a virus locks your operating system or prevents you from running an antivirus, you can still use one of the following bootable disk images to scan your computer:
Download the image on another computer;
Copy the image to a CD/DVD or USB pen drive, and place it in the infected computer;
Enter your computer's BIOS (this is normally done by pressing F2 repeatedly when your computer boots up);
Change your system boot sequence to load from the DVD drive or USB;
Reboot your computer so it loads from the external device;
Launch the antivirus and wait for it to scan and clear your computer;
Remove the CD/DVD or USB and return your BIOS to the original settings;
Install an antivirus as soon as your computer starts up.