Look no further. Enter Microsoft Security Essentials. It's the best of the best anti-virus solution for Windows XP/7/8.
Compatibility
You heard the news. A lot of PC were made dead because of anti-virus software upgrades. Who can you trust for 100% compatibility with Microsoft Windows? It's Microsoft itself!
Reliability
MSE consistently receives highest rating at independent virus test lab AV-TEST.
Compatibility
You heard the news. A lot of PC were made dead because of anti-virus software upgrades. Who can you trust for 100% compatibility with Microsoft Windows? It's Microsoft itself!
Reliability
MSE consistently receives highest rating at independent virus test lab AV-TEST.
Affordability
Virus infection is a long-time headache for the Windows PC platform. Microsoft is releasing this as a free solution for its customers. You can't beat its price tag.
Performance
Did you notice a significant increase in system bootup time after installing a 3rd-party anti-virus software? Take an example, Norton AV is a 250MB download and consumes hundreds of MB of RAM when running. That also means you have fewer memory for your productivity applications.

This is top-grade antivirus software which receives rave reviews across the Internet. Try it out and it's going to save your businesses some nice bucks.
Microsoft Security Essentials continues to be the #1 free AV solution in the market. Well done Microsoft.
I do not see you have a reason to pay for solutions like Norton AntiVirus (USD 49 per year!)