Normally You are not allowed to run multiple yahoo messenger at a time. But if you do a little tweak in yahoo messenger, then you can run as many yahoo messenger as you like in your computer at a time. This means that if you have 4 yahoo IDs, then you can login to 4 different yahoo messenger at a time from a single PC.
To run multiple yahoo messenger at a time :
From the Left Panel Select HKEY_CURRENT_USER
Select Software and then select Yahoo
Now select Pager and then select Test
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).
Alternatively , You can create a new .txt file and write down the following lines there :
save the file and rename the .txt file to .reg file. Now double click the file and your yahoo messenger is ready to run for multiple instance.
A free and very useful utility that allows a yahoo user to run multiple instances of Yahoo! Messenger can be downloaded from here and just after installing it, the user can run multiple yahoo messenger.
To download the utility click here.