My Apple Magic Mouse was “falling asleep” on me in Windows 7. Â Found this post that told how to resolve it.
1. Click on the “Bluetooth Devices” blue icon in the system tray (you’ll probably need to click that little UP arrow first) and choose “Open Settings” from the menu.
2. Under the “Hardware” tab of the resulting dialog, select the “Apple Built-in Bluetooth” device and click the “Properties” button on the lower right.
3. Under the “General” tab in the resulting dialog, click the “Change Settings” button on the lower left (it has a shield icon on it)
4. Under the “Power Management” tab in the resulting dialog untick the “Allow the computer to turn off this device to save power” checkbox.
5. Press OK, OK and OK.
But for me, the Hardware tab was located under “Dell Wireless 573 Bluetooth Module with AMP.”