Here are some tweaks for those who are using Yahoo Messenger (7.x-8.x)

1. Annoyed by the ads?
Start -> Run -> regedit
Navigate to: HKEY_CURRENT_USER\Software\Yahoo\Pager\YUrl
Add the following string key: `Messenger Ad` [wihtout the quotes!] with the following value: “*”.
only add the *

2. If I have 2x accounts?
Start -> Run -> regedit
Navigate to: HKEY_CURRENT_USER\Software\Yahoo\Pager\Test
Create a DWORD key with name of `Plural` with a value bigger than 0.

Note: you have to completely close your Y! Messenger [if you just log out and see a Y! in the traybar it don't gona work, you have to "kill" it completely than run again -> Y! reads the registry only at startup].