Disabling the tabs in MSN Messenger

You will have to edit the registry to remove the tabs in MSN Messenger:

1. If the registry editor is not already started, click on the Start Button and select Run. Then type in regedit in the text box and hit Ok.
2. Navigate through HKEY_CURRENT_USER, Software, Microsoft, MSNMessenger, PerPassportSettings, and then the numbered folder.
3. Right click on the numbered folder and select New and then DWORD Value.
4. Type in DisableTabs as the name of the new key.
5. Next, right click on the new key you just made, DisableTabs, and select Modify.
6. In the value box, key in 1 and hit Ok.

You can now close the registry editor. Once you completely restart MSN Messenger, a reboot may be required for some, your tabs will now be gone.

Note: If you have multiple numbered folders listed under the PerPassportSettings folder, repeat the above instructions for every numbered folder.

:source: Tutorial with screenshots