You can login with multiple ID’s on the same yahoo messenger.
Follow these steps :
* Go to Start –> Run –> Type regedit,hit enter
* Go to HKEY_CURRENT_USER –> Software–> Yahoo –> pager –>Test
* On the right pane –> right-click and choose new Dword value .
* Rename it as Plural.
* Double click and assign a decimal value of 1.
* Now close registry and restart yahoo messenger.
* For signing in with new id open another messenger .
!!!! Enjoy chatting !!!!