Running yahoo messenger and that too one is quite a bigg trouble if you have more than one account and so it is sometimes better to open multiple yahoo messengers at a same time with as many number of accounts
Here is what you need to do some changes to open multiple messengers
1. Open the notepad.
2. Copy the following code
REGEDIT4 [HKEY_CURRENT_USER\Software\yahoo\pager\Test] “Plural”=dword:00000001
3. Save the above code as multi.reg
4. Either double click on this file or right click on it and select merge option. (This will merge this settings into windows registry)