Okay - the worst thing that can happen is that your computer is rendered inoperable. But, we'll set a restore point so that won't happen
First, let me change the instructions in post # 26. I suspect that you do not want anything from Yahoo, if correct, navigate to: C:\Program Files\Yahoo and delete the entire Yahoo folder.
A) Set (create) a Restore Point: 1) Go to: Start>Run, type
%systemroot%\system32\restore\rstrui.exe, and click OK. 2) On the "Welcome to System Restore screen," select "Create a restore point" and click "next." 3) Name the restore point, click "create" 4) Wait for the restore point to be created then click "close." (Note the "\", this is from the key under the backspace key, not the "?" key.)
B) After the restore point has been created, go to Start>Run and type
regedit and, click on "OK." Click the "+" sign by HKEY_CURRENT_USER, click the "+" sign by SOFTWARE, scroll down to the Yahoo folder, right-click on the folder and "delete." Close the registry editor by going to File>Exit.
C) Re-start the computer. Messenger should be gone.