Help with Removing a Pornographic Screensaver

Help! We needed an extra computer just for writting letters and my boss brought one from his house that one of his kids used. When switching screensavers, I saw one that said My Picture Screensaver and clicked on it thinking that it would have pictures of their kids, etc. Instead it contained pornographic pictures. I have tried deleting it and it keeps coming back. I tried removing it with one of the screensavers removal softward and it indicated that it was a Microsoft Protected screensaver.

I don’t really want to tell me boss since the pictures are very explicit, but I also do not want someone sitting down at my computer finding these images thinking that I downloaded them.

Any suggestions?

Thanks in advance for your help