Specifically, for window OS, is there a recommended and/or compatible antivirus software and/or tool one can use to increase the security of the system. The point being, if there is a malware on the system, all the security Tor provides could be in vain. Is Tail in anyway safer to use, having its own OS in the sense of malware presence on the system OS?
Assuming you download and burn Tails from a known virus-free computer, running Tails is much more secure that just adding an anti-virus software.
Tails does not only protect against virus, software keyloggers and similar that may be present on the system OS installed on your computer, but Tails also prevent many possible information leaks Tor Browser cannot protect against (e.g. leaks from other applications on your system).
Remove all malware: Do a complete format and reinstall of your computer, using CD/DVDs you already got/burnt.
Avoid malware: Do not install any untrusted software or games on your computer (e.g. downloaded from warez sites or bittorrent). If you OS tells you a file may be a virus, assume it is. AdBlock Plus plugin to Firefox helps a lot.