hi friends....  
Now you  can open multiple yahoo masengers in a single windows.. By this we can open two yahoo mesenger ids.
Firstly ,you will need to access the registry editor to change the properties of the yahoo mesenger propeties.
To do that you need to click on the  start button , go to run and type regedit in the box then press  OK.
From the registry editor locate the HKEY_CURRENT _USER folder and go to the Software folder. Next, you need to look for the Yahoo folder and click on pager. Right click your mouse and click on the DWORD option.
Change the value name to plural and you may choose form numbers one to three for the value number. And click the OK button to save the changes done.
Now  you may enjoy a multiple messenger. Enjoy chatting!