is it windows 8? it's called a help tip
To permanently disable help tips you can do this via editing the registry however if your not comfortable doing this you can download a file from somewhere, i'll have a look for it.
Update found file on here:
http://www.eightforums.com/tutorials/31 ... 8-1-a.htmlOr follow these instructions if you can as i've not used that file before so can't say if it's safe or not
http://www.hongkiat.com/blog/disable-wi ... help-tips/You can control other notifications by doing
1, pressing windows key and L together
2, Click on 'change pc settings'
3, click notifications and change the ones you want there