If data is less important, you can always trust Microsoft Security Essential. However, if data is really important and system handles financial records along with sensitive data (be it home computer or office), look into Kaspersky Internet Security.
Microsoft Security Essential -> Is free and supports Windows XP SP3 to Windows 7. Its an integral part of Windows 8
Kaspersky Internet Security 2013 -> Its one of the best in business, but kaspersky sales team knows India and they sell 3 User version at Rs. 750/- only, meaning effective price per user is Rs. 250 for one year
. You can always buy 3 user version and share it with your friends so price comes with effective of Rs. 250 only.
Update
No matter what AVS or security you use, they are as good as no to be present without regular update. So regular live internet connection is needed, both this software will update them self in back ground without disturbing you, unless there is something wrong
Install in fresh system
If you are installing AVS, try to install in a fresh installation of OS, as if OS in which you plan to install the software on, already having virus infection, it becomes really difficult to have a fully OK and healthy system.
Thanks.
