The only answer I have to this question is-YES you do.
Regardless of whether you are a novice or a pro in the security field everyone needs an antivirus. Antivirus is obviously not your first line of defense (Firewalls are) but they are an integral part of your computer's security.
As a student for some time in malware removal courses I have seen and helped people who have been infected to the extent that they wouldn't even able to connect to the internet or faced regular computer crashes.90% of them are users who click every random pop-up that comes their way or download cracked software uploaded on random websites but the remaining 10% are users think they don't need any antivirus as they -according to them - know a lot about security and never click on pop-ups and test every software firstly on their virtual machines befor transferring it to their main desktop. But what these people forget is that antiviruses help in early detection of known malwares and a regular scan (I prefer one scan every fortnight) helps to check any subtle infection.
Of course, antiviruses don't help with every infection and with malwares like Antivirus 2007,8,9 series or cool web search you need specialized tools but antiviruses act as an external support to these tools and help in removal of remnants of these infections.
The other question that users ask after you convince them to use an antivirus is - Which is the best antivirus?
Well, there's a very thin line between an average and a good antivirus. And this thin line is often the scanning speed than malware detection. Most of the antiviruses don't have much difference in malware detection rate and like I earlier said antivirus softwares help in removal of small infections only, for some malwraes you need specialized tools. So, having any antivirus is better than having none.
There are some good free ones like Avast , AVG and Avira antivir (Avast is my preference) and excellent commercial ones like Esset NOD32 and Kaspersky (I'm hearing some good reviews for the latest Norton antivirus too). The choice of using a free or a commercial antivirus depends on the user. I personally don't feel like spending my money over a commercial one if a free antivirus like Avast does almost the same job.
Now that I've written so much about antiviruses I think I should advertise the importance of firewalls, anti-spywares and hosts files too (Though I'll be writing a document on how to keep your computer safe in the coming days)
Firewalls -like I earlier said- are your first line of defense. They keep most of the pop-ups and hackers away. Windows firewall is a very basic firewall (No hard feelings microsoft). For better security you need a good firewall. An excellent free one is Comodo Firewall. Zone alarm is also a very good firewall though I would rather go for it's commercial one.
I won't dwell much in to anti-spyeares except giving links to some good ones. A combination of Spybot and a-squared is believed to be a good choice to go for. I personally use Spyware Terminator and never had any problems with it. There are also good commercial ones like Spyware doctor but I would rather choose a free one like the case in antivirus.
Lastly I would advice you to have a good hsts file. I'm using MVPS hosts file which is the best hosts file available today. It block all pop-ups and random advertisements.And again it's free If you don't want to follow my advice on antivirus, firewalls and anti-spyware atleast go with the hosts file.
Using a good anivirus, firewall, anti-spyware and hosts file(MVPS) -preferably all free- along with a little common sense is enough to keep you computer safe.
And if you still get infected there's an excellent group of forums from ASAP which help users with their malware issues and also train users in malware removal- all for free!
Now I just want you people to share you opinions with the rest of the community or just tell me was this useful. Any reply is greatly appreciated=P