Okay, if you wonder how to run two yahoo messenger, ie using yahoo messenger with multiple login or id here is the way to do it:
First... Click Start -- Run -- type in 'Regedit' -- click Open. A new window will open. Browse 'HKEY_CURRENT_USER'.
Then .. click 'Software' ... click 'Yahoo' .. then click 'pager' ..
And lastly click 'TEST'
Now you can see an icon ab with the name 'default' on the right column.
Right click on that screen ..
Click NEW - 'DWORD value' and name it as 'PLURAL'.
Then .. double click on 'PLURAL' and modify it ..
Change the 'Value data' from 0 to 1. Click OK to close and it.
Now you can open as many yahoo messenger in your PC or computer.