Your problems have only begun. Yahoo tool bar is there to stay unless you get all the info to uninstall it. Google Yahoo Toolbar and read all you can about this and find out how you can rid yourself of it. You've probably gotten it into a file that will clone itself when it's deleted and thus, it can't be removed. But it can when dont the right way. Just be patient and read all about it and soon you too will become proficient enough to remove this evil substance.
You can always reformat your computer and then you'll know for sure that you've ridded yourself of this evil resident.