I think it should just be one of those core development rules, that you can't create any desktop feature that known as balloons.. There's so many bad connotations - my desktop has 'ballooned', memory consumption has 'ballooned' or the OS has just ballooned with useless features. Anyway, if you're like me and work with a notebook with USB hub for your phone, your mini-mouse, your USB memory key and you use wireless and you use synchronized folders and messenger, then the balloons in the system tray surely drive you crazy. I mean, does it really add much to 'balloon' the fact that a network cable has become unplugged (uhh, yea, I just unplugged it)

or that I've connected my “USB Human Interface Device” (aka a mouse!). OK, OK, I'm sure that these things help sometimes, but really, every time I plug in my mouse!!!?
But alas, there is a solution.
- Navigate to the following subkey:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Explorer\Advanced
- Right-click the right pane, create a new DWORD value, and then name it EnableBalloonTips.
Double-click this new entry, and then give it a hexadecimal value of 0.
Quit Registry Editor. Log off Windows, and then log back on.
Ahhhh, joy!
http://support.microsoft.com/default.aspx?scid=kb;en-us;307729