Which browser are you using? It's usually easy to manage your home page and search engines. Has the Ask toolbar also been installed?
May I recommend Unchecky which will assist when it comes to installing software so that you don't end up with unwanted extra bits and pieces in future http://unchecky.com/
Thank you all for your responses, a weekend visit by my 12 year old nephew and job sorted. I don't understand what he did but things are back to normal,