In a cybercafe, have you ever wondered how to find the Yahoo! id of a beautiful chick or a incredibly sweet, smart, sexy man chatting in the next cabin?? If the answer is YES, this Notepad is just for you.
In general, whenever someone uses their Yahoo! id to log-in to their account from a computer, it automatically gets stored in the Yahoo! profiles. These stored ids can be easily accessed from the registry editor as below:
1. Go to Start–>Run… and type regedit and click OK, which open the registry editor window for you.
2. From the left pane go to the registry key
HKEY_CURRENT_USERSoftwareYahooProfiles and check its sub-folders. There you can find all the yahoo ids used on the PC. 
That’s it!! You have got what you wanted.
Hope this helps…
Try it yourself and post in your valuable comments.
Note: Don’t use this trick for any harassment or spam.