A computer technician at work recommended several different adware removal programs, most of which were free to download. Sometimes free isn't really free, though. A few of them keep putting pop-up ads of their own, recommending that I upgrade to a paid adware and spyware remover service. If the upgrade is expensive, I usually delete the free program and install something else.
The technician also recommended downloading a program called a "decrappifier" and running it whenever you get a new computer. It detects and removes trial programs, pre-installed games and other items that are unnecessary and bloated. Once you remove all of those memory hogging programs, a lot of adware and spyware goes with them.