How to remove iplay.com search hijacking?

A few months ago someone using my computer installed an iplay game, after a few simple operations I was able to remove the software from my machine, including the tool bar and home page hijacking. but even after having removed everything, typing text into the address bar, that wasn't a proper url, would redirect me to the iplay website instead of the usual google search site. Recently I've discovered that iplay has hijacked the search field in the firefox homepage, I'm talking about aboutHome.xhtml