To disable these balloon messages follow the steps below:
1. Open the Registry Editor by clicking on Start -> Run and running REGEDIT.
2. Navigate to the following location: HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Policies\Explorer
3. Right-click in the blank area of the right-hand pane of the Registry Editor and create a new DWORD Value by selecting New -> DWORD Value.
4. Name this new DWORD Value NoLowDiscSpaceChecks
5. Double-click on the new DWORD value and assign it a value of 1.
6. Close the Registry Editor and restart the computer.