Please ... why?
He is wrong, the Windows built in firewall and MSSE work fine together. And are all the security software that you need. Windows 7 is pretty secure.
Do NOT buy some random “antivirus” software off the net. Most are crap or outright scumware. The best way to protect from malware on the web (after you have installed MSSE) is described here:
http://www.malwarehelp.org/how-to-effectively-prevent-malware-hosts-file.html
It is just a bit technical (you have to download a file and put it in the right folder with the right name) but not hard at all. Just follow the instructions.
A home or small office router, wireless if you wish is a good addition. Their default settings are pretty secure and they are easy to set up. It makes your pc pretty invisible to the outside world. If you get a wireless router turn on the wireless security (wpa or wpa2).