his is what you should do first:
Go to your browsers' settings and choose add-on/extensions.
Search for anything that is related to ask toolbar (and also any other suspicions file name) and remove it.
Again from the setting, change your homepage back to normal (that is if it has been changed)
Open Control Panel and search for any program or file with the same name and remove them.
Open your windows Explorer and search again for any left file or folder containing ask in their name.
I suggest you read this ask toolbar removal guide:http://www.virus-delete.com/en/guides/browser-hijacker-removal/20130814-how-to-remove-ask-search-toolbar-through-isafe-virus-removal-tool.html
if you can not figure it out.