Download ym8multi.zip, extract it and run “ym8multi.reg” contained inside the archive. Once the registry is patched, you can now starting and running multi Yahoo! Messenger with different login or Yahoo! ID accounts.
If you want to uninstall the patch/hack, download the ym8multi_uninst.zip uninstaller which contains ym8multi_uninst.reg. Once double click on this uninstaller registration registry value file, it will edit the registry value and set it to disable the ability for Y!M 8 to launch multiple copy of instances.
If you prefer to edit and change the registry setting yourself manually, without using the above registry registration file, simply launch the registry editor (type regedit at Run command), and navigate to the following registry branch:
Then, on the right pane, right click on the registry editor and select New, then create a new DWORD registry value. Name the new registry key as Plural, and assign it the value of 1 (decimal). If some case, the value of 2 should also works.
To disable or disallow multiple instance of Yahoo Messengers, simply change and set the “Plural” registry key’s value to 0, or delete the “Plural” key.