Unwanted Yahoo Appearance!

[JandyAF]

Help! I have a Mac OSX with Safari browser and Hotmail, and suddenly today a Yahoo screen has kept popping up when I check my emails. I do have a Yahoo bookmark but never use it preferring Google. The Yahoo's an absolute nuisance, and it almost instantly replaces any email I look at (received or sent), without me doing anything, and I can't get rid. In addition to this a new toolbar has appeared on the desktop under the usual one, which seems to be there permanently now. My daughter was on the computer playing games yesterday, but she would not have been on Hotmail as she doesn't have the password. The Yahoo page is headed "install converter our toolbar notfound", and then says "The requested URL 'http://InstalllConverter.OurToolbar.com/notfound/?hsimp=yhse-001' cannot be found or is not available. Please check the spelling or try again later." Then follows a load of links re toolbar downloads etc.

[Buenchico]

I'm fumbling in the dark here but there's a chance that something below might help, so I'll post anyway:

In Safari, check to see whether there are any unusual extensions listed as being present. (I'm not really familiar with Safar but I think that you need to look under the 'Help' menu, for something like 'Installed plug-ins' and/or 'Extensions' and/or 'Add-ons').

Also take a look in your list of installed programs and see if there's anything relating to Yahoo! that needs removing:
http://www.wikihow.com/Uninstall-Programs-on-Mac-Computers