As Dan bhai said,
yes Eset ss is good one ,
when compared NAV it won't take much resources or slow down system.
some free AV while cleaning the virus deletes system files in turn system hangs up.(no use of the Anti virus-- when it cleans virus and hangs u r system).
important- for extra protection don't install more than one antivirus, since small part of the AV-program resides in the memory makes conflict with the other one. (this will also result in computer hang)
when buying Eset you have to choose
Eset-AV(antivirus) or
Eset-ss(smart security). later one is best because it will be having antivirus with firewall feature.(useful for online activity scans mail etc..,)
just checked esetindia , rupees it seems better
.
http://www.esetindia.com/shop/new/home/ or u can go to computer market and purchase.
with cheers
narayan.