If you ask ten different people, what they feel is "best", you might get ten different answers. Try using the search function at the top of the forum, and enter "best antivirus". Do the same with malware/adware. The search should yield you, a countless number of threads, where members have expressed their opinions.
You haven't mentioned which operating system you're using. I can suggest a couple of each, but make sure they're compatible with the system you're running, prior to installing them.
These are all free, with paid versions available:
Avira AntiVir Personal - FREE Antivirus
Avast! Antivirus Home Edition
SUPERAntiSpyware FREE Home Edition
Best of luck..
I recently got a major problems with my laptop. Can anyone tell me which antivirus/adware soft is better?