Uninstall Yahoo Messenger! using this program >click HERE
Before starting to uninstall Yahoo messenger be sure that it is not running. So check your taskbar at the bottom of your screen and near to your system clock, right click on its icon and select "Exit". Then select the program and start the "Uninstall" command. Uninstall process with Revo Uninstaller Pro starts the uninstalling wizard, which shows you what is happening on every step of the uninstalling procedure. During the uninstall Revo Uninstaller Pro tries to run the built-in uninstaller of the uninstalled program, if it works properly let it to do its job, but if it is not working properly here you will see an error message that you will have to skip ( ignore ). Then select an uninstall mode and press "Scan" button to continue further to the next step of the wizard. After the scanning completes you will see the leftover Registry items, files and folders, review, verify and delete them.
After you uninstall Yahoo Messenger ..install the latest version from Yahoo Site->http://xp.yimg.com/gj/msgr/11/suitega2/msgr11us.exe