If i may class the users, i will say it would be something like this: 1st level, threat vulnerability = low -Check e-mails, and -Send e-mails, and/or -Only browse the web, and/or 2nd level, threat vulnerability = medium -Same as above, and -Chatting using Instant messengers, such as Yahoo Messenger Users categorized in the first level are the one most suitable to use free security applications, but users in the 2nd level may need to be more cautious if they also choose to use free security software. Free Anti-virus Free AV from Grisoft or AVG is my first recommendation. I have experiences using it before, it had served well defending my PC from infections. You may get your own copy of AVG by clicking on this link : Get Free AVG . Installation and usage of the program is quite simple and well organized. You should have no problem using this piece of software. It supports email scanning and on demand scanning. My second recommendation is Bitdefender free edition. But since Bitdefender only supports on demand virus scanning, i wouldn't suggest for frequent Internet and instant messenger users, even the provider seems to think it that way.

BitDefender 8 Free Edition is an on-demand virus scanner, which is best used in a system recovery or forensics role. If you are on an "always-on" Internet connection, we strongly advise you to consider using a more complex antivirus solution.

You can download the free copy of Bitdefender at : Get Free Bitdefender Free Spyware Scanner/Remover Again recommending another free security application from Grisoft, Ewido. Evaluating Ewido for all the time it had protected my PC from spywares, it must say, it is an awesome free software. Updates are frequent and it can even detect unknown threats, which is a plus to the product. Try it for yourself : Get Free Ewido Another spyware scanner and remover that i would like to promote is the AdAware from Larasoft. It is popular free software, most probably you have already heard about it. AdAware boast about it's Code Sequence Identification (CSI) technology, which allows the software to detect unknown malware infection. Other than that, Larasoft also offers addon's for Adware at it's website. Just choose which addons that you like, download and install it. Like Ewido, AdAware hasn't yet failed me when it comes to detect irritating spywares in my PC. Dont take my word for it, download and test it : Get Free AdAware That are the four main free defence software that i highly recommend. Just keep in mind, i wouldn't recommend them if i haven't personally tested and used them in a period of time. But just a reminder from me, no one security software can protect you from all the threats out there in the Internet, my suggestion is, use a couple of software to give your PC more protection. In this case, unfortunately for the Anti virus, you may just choose one, but for the spyware protection, you may use both. Like the old saying goes, two heads are better than one :)