To remove cookies on a PC, open up the internet browser. Then,
depending on the version and type, you need to find the Internet
Properties tab. Once you click on that, you should be able to find an
option to "delete files" and that will remove all cookies and other
stuff you don't really need to keep on your computer.
Instead of Stop Sign, I would recommend downloading two free programs
-- Spybot and Ad-Aware. These are two programs that my brother (who
goes around fixing PCs for businesses for a living) recommended to me,
and I haven't had any more trouble with malware. These two programs
need to be run about once a month to keep malware off your computer.