Copy the following text in notepad and save it as “filename.reg“
Name it anything you want, just make sure that the extension is .reg

Now run the saved file by double-clicking it.
Simple

Windows Registry Editor Version 5.00
[HKEY_CURRENT_USERSoftwareYahoopager]
“Tabbed IM”=dword:00000001

To turn off this, repaet the above procedure with this text

Windows Registry Editor Version 5.00
[HKEY_CURRENT_USERSoftwareYahoopager]
“Tabbed IM”=dword:00000000

Works in Yahoo Messsenger Version 8.1