Shoutbox

Open up Windows Task Manager (CTRL+ALT+DEL), go to Processes tab. If msnmsgr.exe is running, click it then press End Process (Note: Plus! is integrated into Messenger, so there is no seperate process for Plus!).

Now that Messenger is not running, try running the Plus! installer again.

If you still receive an error, screenshot it, paste into paint, crop it, save it, attach to your post.