help - alien websites have taken over my internet favourites

My teenage daughter downloaded some free games onto our computer - as a result when ever I click onto the Favorites button - the first half dozen or so "favorites" that appear are sending me to dozens of sites for casinos, games, shopping, holidays etc..These favorites cannot be deleted from Favorites and if I try to organise them - they don't appear in the Organise favourites box! They also don't appear in the favorites as shown in the My Computer/Documents and Settings etc. I continually run ad-aware to get rid of the tracking cookies that are now flourishing at a huge rate but does anyone have any idea how to delete these nasties from Favorites? Thanks for your help...