If you have Anti Malware Doctor installed on your machine, it’s spyware/virus. You will receive messages such as virus detected or virus detected which may dial out to an expensive telephone number etc etc, and will prompt you to purchase the software to remove.

Download http://www.superantispyware.com/ and scan your machine. There are lots of spyware removal software available on the Internet, but this is one which picked up and removed Anti Malware Doctor, where as a couple of other removal software I tried did not.