PSFree.exe is Panicware's popup stopper. Everybody hates the pop up/under ads but they're a very high paying format and provides thousands of dollars of additional funding for sites like this one. More information here.

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Pop-Up Stopper Professional is the latest in Panicware's award-winning pop-up ad-blocking product line. The only product to provide native support for AOL, MSN, Internet Explorer, Netscape, Opera, SBC Yahoo!, CompuServe, WMConnect, Juno, NetZero, Mozilla all in one software package!