Keep in mind most of these have spyware and adware plus browser hijackers....you may want antispyware programs like webroot or counterspy....
Don't click the screensaver ADS. "Goodle" it....and be sure to read the EULAS. They may mention "Ad supported software". Also make sure you don't allow ActiveX controls and DO NOT USE SCREENSAVERS ASSOCIATED WITH THE STARWARE TOOLBAR FOR INTERNET EXPLORER!