The number of free antivirus is increasing...but whether they are good a not is another issue.
Protecting your com is important,therefore having something to protect is better than having nothing to protect.Even Windows Firewall is such an important thing that you must actually leave it on cause it is just better than nothing.
My recommended solutions are Avira Antivir,Avast or Microsoft Security Essential.This 3 did a good job in protecting your com without a cost.There are much more other choices outside as well.Here are the lists:
AVG Antivirus Free
Rising Antivirus (Full protection just like Avast)
PC Tools Antivirus Free Edition
Panda Cloud Antivirus (no update of definition require,you only need internet)
Digital Defender Free (new antivirus,have the same engine as PC Tools Antivirus)
Immunet Protect + Clam AV (no update of definition require,you only need internet)
Comodo Internet Security (a free internet security which bundle Antivirus and Firewall together)
If you don't mind coming out money...well Kaspersky (around SGD31 for one year one PC license) is still your choice.
Even if your antivirus can't detect and clean a virus...there is always a solution to it.First of all,please confirm the virus name by uploading the suspected file to Virustotal and check which antivirus finds it.If by chance Kaspersky also able to detect it,then the ultimate solution has come.Go get the free Kaspersky Removal Tool,it is a tool that is able to scan and remove (but no real time,cause this is just a removal tool) malwares that are infecting your com.
Another solution is try scanning with Malwarebyte Anti Malware or SUPER Antispyware (both are free,with only on demand scanner) to see whether they can detect and remove your threats.
So my friends,if anyone of you suspected of being infected and don't know what to do...you can come find me.
Also,next week i will be damn busy...as well as the following week...hell is starting.