Avira, and or AVG(avast) both have free versions you can try arent resource hogs and are better imho than any other offerings on the market atm. I personally dont care for Trend as you tend to get a lot of bs messages and it is a resource hog. Tou can google Avira or AVG 8.5 i think is the latest version, I'd know for sure, bu am offshore at work, and cannot look
at my PC to ensure I am correct. Also I would download Superantispyware (superantispyware.com) and anti malwarebytes as well as c cleaner. SaS is a good utility for removing malware and viruses as is Anti Malwarebytes, and C cleaner (piriform.com) is a utility that helps keep windows clean of unused file extensions dll's etc as well as getting rid of cookies and other issues.
Good luck and congrats on your new pc.