Existem várias formas de desativar a chave do Windows, conforme visto em esta página
Opção 1: Editor do Registro
- Click Start, click Run, type regedt32, and then click OK.
- On the Windows menu, click HKEY_LOCAL_ MACHINE on Local Machine.
Double-click the System\CurrentControlSet\Control folder, and then click the Keyboard Layout folder.
On the Edit menu, click Add Value, type in Scancode Map, click REG_BINARY as The Data Type, and then click OK.
Type 00000000000000000300000000005BE000005CE000000000 in the Data field, and then click OK.
Close Registry Editor and restart the computer.
Opção 2: AutoHotKey
Download AutoHotKey from http://www.autohotkey.com/
Run it, then right click on its icon in the taskbar.Select 'Edit This Script' and it'll open the default script in Notepad
Somewhere between the comments (which are marked with semi-colons) add the following:
~LWin Up:: return
~RWin Up:: return
Now just save the file, right click on AutoHotkey again, and select 'Reload This Script.'