Try seeing if you have a program called that in your system. To do that go:
start menu-> control panel-> add remove programs-> and then check if that is installed on the PC and if it is remove it.
Another way is to download Avast antivirus from download.com. It will take away any potentially harmful thing including the pop up you are getting. Also try ZeroSpywareLight and that might get rid of it.
I wondering if you are running windows 2000. If so, there is an option that allows certain annoying pop-ups that tell you to pull up porn every 5 seconds. There is a way to disable them, but that doesn't seem to be your problem. If you want I could post how to do so.