What are the best free anti virus / malware tools?

Question

I just reformatted my PC due to the age old problem of getting as slow as hell. It's been a very long time since I last looked at antivirus / spyware tools (just kept what was on my old PC for years updated) so I wanted to know what's the best anti virus and malware tools at the moment. 

Answer 1

try microsoft security essentials. http://windows.microsoft.com/en-us/windows/security-essentials-download

Answer 2

Top free AV products
BitDefender Free, ZoneAlarm Free, Adaware Free AV, Commodo Free, Avast, Avira, AVG

Best Paid:
Kaspersky, eSET, and BitDefender as the top paid AV products.

Malwarebytes Free version is something everyone should have as an on-demand/backup scanner. It doesn't have a real-time component, you have to get the paid version for that, so it can't be your primary, but nothing beats it as a secondary.

Anti-Adware/PUP software:
Adaware by Lavasoft, Spybot Search and Destroy, Superantispyware, Malwarebytes all offer free and paid options. Other top products: Spyware Doctor, Double Anti-Spy Pro, Avast Grimefighter, Vipre Antispyware (formerly Sunbelt's CounterSpy), Bullguard

It used to be that antispyware were standalone products to run along side of AV software, but most AV software has added fairly good antispyware to their products. Likewise, many of the antispyware products have had full AV programs added to them (Adaware is a good example of this).