I have recently been getting these pop up on my computer that say that a recent attack has been detected. When I click on them it takes me to a website for software that cleans your history. Sometimes the just the website itself pops up. Also an add becomes my background sometimes. Any idea why this is happening and how I can stop it?

You have been hijacked. Download and run HijackThis from -

http://www.merijn.org/

Post the resulting log file here for analysis -

http://www.hijackthis.de/

"Fix" the entries it identifies as nasties unless you know what they are and wish to keep them.

Chris B