Complex sentence: CoolWebSearch is a family of extremely persistent malicious programs which install themselves on Windows computers running the Internet Explorer web browser and then redirect the browser's home page to the search engine at coolwebsearch.com (the site webcoolsearch.com appears to be closely related).
Split into simpler sentences: CoolWebSearch is a family of extremely persistent malicious programs which install themselves on Windows computers. They then change the Internet Explorer homepage to coolwebsearch.com (the site webcoolsearch.com appears to be closely related).