Steps for multiple logins in yahoo!!!
1. Start ==> Run ==>> Type regedit,hit enter
2. Go to HKEY_CURRENT_USER -> Software -> Yahoo -> pager -> Test
3. On the right pane ==>> right-click and choose new Dword value .
4. Rename it as Plural.
5. Now double click and assign a decimal value of 1.
6. Now close registry and restart yahoo messenger.
7. Open another messenger for signing in with new id .