Well, i can understand your compliant. The only way to prevent such annoyances is to run in a limited account with windows. That will prevent most malware from getting to your computer. W7 has made great strides with "Standard Mode", otherwise i recommend running an anti-virus.
My recommandation for you would be Sunbelt Vipre. Vipre is very light on resources and gives very few popups and its very cheap.
http://www.sunbeltsoftware.com/home-home-office/vipre/
My dad has it installed on his netbook with no issues at all.