Here is "FEW" tip

Avira AntiVir Antivirus

Commodo or ZA Firewall

Spybot Search & Destroy 1.4

Best part is All of them are FREE

If for Paid:

NoD32 Antivirus. [Nothing Beats this one in lightness and detection ratios]

ZA Pro Firewall

Spybot Search & Destroy 1.4 [Y the best software for spyware busting is FREE]

Kaspersky for KIS its Rs. 850/- incl TAX in Kolkata, where as NOD32 only antivirus is Rs. 1600/- + TAX

ClamAV. Its completely free (with source code):www.clamav.net