Mary wound up getting a program called Trovi installed, and she can't get rid of it. Trovi is a lot like Conduit, and it's a browser hijacker that often comes with free software. Some don't think it's malware, but if it tricks the user into installing it and makes it difficult to be uninstalled, then it's definitely malware. And shame on CBS, which owns download.com, for allowing this junk to be installed onto people's computers. Mary can remove it in Add/Remove Programs, but she'll also have to change her browser settings or it could come back. She'll need to remove the extension, tool bars, and change the home page.
Here's a link on how to uninstall it - http://www.lavasoft.com/mylavasoft/company/blog/how-to-remove-trovi-search
She'll probably have to uninstall several other things too. So search for Add/Remove programs by date and then uninstall the things she doesn't recognize that were installed around the same time. Conduit is probably there too.