Isso parece desativar todas as dicas de balão; Não tenho certeza se você pode desativá-lo apenas para eventos de rede.
To disable balloon tips in the notification area, follow these steps:
1. Click Start, click Run, type regedit, and then press ENTER.
2. Locate the following subkey:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion
\Explorer\Advanced
3. Right-click the right side pane, create a new DWORD value, and then name it
EnableBalloonTips.
4. Double-click EnableBalloonTips, and then give it a value of 0.
5. Close Registry Editor.
6. Log off Windows, and then log back on.