Most of the Linux distributions are free. Linux is more a kernel from which various operating systems have been designed. Each of these OS is called a linux distribution. Currently there are hundreds of distributions-both free and commercial.
You can gather more info. at
http://en.wikipedia.org/wiki/Linux
http://www.linux.org/

You can get all the Linux distributions at
http://distrowatch.com/
 
Since you have never used Linux I suggest you start off with Ubuntu which is a free Linux distribution. It's very easy to use.
http://www.ubuntu.com/

The download link is here:
http://www.ubuntu.com/getubuntu/download

It's a 700 MB iso. If you have a slow internet there's an option of torrent download on the page too.

It can be used with windows. However you have to partition the disk before installing it. Here are some links to help you out.
https://help.ubuntu.com/community/WindowsDualBoot

If you have problems in dual booting you can install Linux on a virtual machine.
http://cmsproducer.com/Ubuntu-Linux-Windows-VMware-Server
http://www.psychocats.net/ubuntu/virtualbox

according to the top notch security researcher's and network audit engineers' and security manager's they are opting for going restart of Internet from begining, as the sql injections, clickjacking, spywares, virus, spams, botnets, are having there own virtual net and spreading each and every second , most of them should be knowing that an unpatched windows is not safe more than 5 min of its connection with net
means and unpatched windows machine gets effected within 5 min, and the thing to worry abt the restart of NET is , how safe is our data, info and how is the world going to cop with the new security standards....
we just need to wait and watch

My response isn’t particularly a specific AV related one. Although I do believe it is still worthwhile, as yes it won’t catch everything, but it will catch what it knows about and surely this is better than nothing.
Moving forward we will see things moving more and more to heuristics and behavioural based, as opposed to signature, but it will always have its place.

As with everything, and especially with security what tools you use, and the level of tooling will should depend on the risks and associated cost.
It can be difficult to strike the right balance, but availability and usability is something I feel people often overlook, just focusing on the confidentiality and integrity aspects.

thanks for both Sgt and Tim, i know gov are still dealing with old IT structure they are least botherd for upgrading it cause they just have time and money for investing in physical security , but todays war is no more physical its more over virtual, gov's have there more trust on there physical security at border or in some other continent, but wht abt the VIRTUAL, they need to trust there IT guys too who have been pointing there fingers towards there machine or network, todays world is taken over by SPAM, SCAM, TROJAN, BOTS, BOTS have become more clever and more tough, top ppl who sit behind the table have to open op there minds rust of there old brains and think towards todays senario. lets cross our fingers...

Ne0,

On the government side and business side of things, there is a tradeoff between security and functionality. It cost money to upgrade hardware/software. And then depending on the environment, it must go through testing to ensure that the upgrade doesn't break anything. Of course if there is a legacy application, it would need to be rewritten. That too costs money. Most businesses and even government contracts have a finite amount of funds budgeted for their projects. Then of course there is the trade off for down time to actually do the upgrade to the production systems. This cost money for the upgrade itself and cost money in lost productivity while the system is down and training time for employees once the system is back up.

Think of the switch people made going from XP to Vista or Office 2003 to 2007. Users had to learn how to do things over that they used to do without thinking about it. This is lost productivity. We live in an imperfect world and we can only do our bests with regards to security. That's why we are needed. We are there to keep things from getting too bad and impacting the businesses we support.