Well since it sounds like you have a genuine copy of windows, you could use Microsoft security Essentials, which you can download for free. Other good programs are AVG and AVAST, which as you know is a pretty good free AV.
As far as spyware protection, I would recommend sticking with Malware Bytes, that's the one I currently use.
basically this, and to give my opinion on this, I use a combination of superantispyware and spybot search & destroy.
Both of them are free and do a more than effective job at keeping your machine clean
Although I never liked avg, I always felt like they were missing something, even if they weren't
Sent from my HTC Evo