How To Get Antivirus Firewall Software
Antivirus and firewall software are two distinct methodologies to secure your computer against being compromised. A firewall blocks access to your machine, while an antivirus scans your machine for signs of a virus and deletes them. A third type of product is an anti-spyware which is specifically targeted to stop unwanted ads and monitoring of your computer activity. Antivirus firewall software is incorporated in a comprehensive security suite. A virus will arrive gain access to your computer either by exploiting a flaw on your system or by being activated by the user by pretending to be something else.
You may have come here because you think that your pc is already infected with a virus as it is running slowly or showing popups when you browse the net, it may be instead that you are infected with spyware, take a look at fixing spyware infection.
It is important to have a firewall and antivirus software otherwise you computer may be taken over. Once your computer is compromised in this way then the intruder has the ability to do anything they want with your machine, this includes reading all your emails, making you see popup adverts constantly, identifying your passwords, reading all your documents, sending out spam email from your machine potentially infecting your friends computers, copying illegal files to your machine etc.
Windows XP comes with its own firewall since service pack 2. If you have not already then enable windows update then it may be prudent to do so now, note though that first make sure that your computer has enough free space. then go start-> control panel -> system -> automatic updates, and check it is on automatic. Once it is installed you should see a shield in your system tray (bottom right), click on this to see if the firewall is active, if it is not then activate it.
Here are some commercial and non-commercial options for antivirus firewall software: