If you've installed Yahoo Messenger it starts up automatically with Windows. If you disable it with msconfig from starting up it rewrites the entry and the software starts up anyway. There is another way to prevent it but you have to log in… and strangely, I don't want to… I'm a sysadmin and I only installed it for an image but I don't have a yahoo messenger account. So that's no option for me. I did found a way however:

• Close down Yahoo Messenger
• Startup the registry editor by typing 'regedit'
• Go to
• HKCU\Software\yahoo\pager
• And set 'Launch on Startup' to '0'
• Then, to be sure, go to
• HKCU\Software\yahoo\pager\defaults
• And set 'Launch on Startup' to '0'
• Then, to disable the software from still starting up, go to
• HKCU\Software\Microsoft\Windows\CurrentVersion\Run
• And delete the key that starts up Yahoo Messenger.

This will do the trick but to be totally sure check also this hive:

• HKLM\Software\Microsoft\Windows\CurrentVersion\Run

if there is any key about Yahoo. If so, delete it.

• Start Yahoo Messenger
• Sign in with your Yahoo ID
• In the menu bar, click Messenger and then go to Preferences
• In the window that appears, uncheck ‘Automatically startup Yahoo Messenger’
• Press ‘Apply’, ‘OK’