Oh dear????????

Yesterday I when I was downloading music I downloaded a WMA file, when I tried to play this I was asked to agree to terms and conditions in order to install a programme. I decided to cancel the operation and delete the file. However today when I logged on to the internet I was immediately confronted with a pop up which got through the filter and there is now a tool bar with unusual links just below the address bar. I think this must be as a result of trying to play this file yesterday. I have tried everything I can think of to sort the problem, but I don't know much about computers. Does anyone know how I can solve the problem?