You don't need anything extra on your Windows system apart from an anti-virus (Windows Defender is a minimal anti-virus installed with Windows 7 but you need more).
Most of the anti-virus companies sell a package with their own Firewall software but the Windows integrated Firewall does a good job already.
I'm quite impressed with Microsoft Forefront. Last week a friend asked me to install a doubtful version of Photoshop that someone else had given her on a USB key. As soon as I opened the folder Forefront came up with a stern warning that it contained a known hacker program - not even a virus - and asking if I wanted to continue. I had no difficulty in explaining to my friend why I was not going to install this copy Photoshop on her nice clean system.