You can login with multiple id’s on the same yahoo messenger without any download or patch .
Follow these steps :
1. Go to Start —-> Run . Type regedit, then press enter .
2.Navigate to HKEY_CURRENT_USER ——–> Software —>yahoo —–>pager—->Test
3.On the right page , right-click and choose new Dword value .
4.Rename it as Plural.
5.Double click and assign a decimal value of 1.
Its done successfully!!
now open as many yahoo messenger and use them with multiple login..