Windows 8.1 Device Manager now showing ACER Device rather than Android Device for Google Nexus 7

First try this simple procedure provided by @volodymyr-rybak:

Open ‘ACER Composite ADB Interface’ and select ‘Update Driver…’, in
the opened window select ‘Browse my computer for driver software’ then
‘Let me pick from a list of device drivers on my computer’ in the list
select ‘MTP USB Device’ and click on Next button.

This is what worked for my Nexus 4.

1. Disconnect your Android device.

2. Disable USB Debugging in Developer Options.

3. In the Device Manager (on PC), click on View --> Show Hidden Devices.

4. Double click on the entry for ACER Composite ADB Interface to open Properties.

   Click on the Driver tab and then on Roll Back Driver. This will uninstall the problematic drivers.

   If the ‘Roll Back Driver’ option is grayed out, then click Uninstall. In the confirmation pop up window, select Delete the driver software for this device and then click OK.

5. Do this for all the instances of ‘ACER Composite ADB Interface’.

6. Shut down your PC. And start it again.

7. Now reconnect your device. Your PC will recognize it as a storage device.

8. Re-enable USB Debugging.

9. If it again shows up as ‘ACER Composite ADB Interface’, then repeat (4) and (5) to roll back the driver update.

10. Or… Open ‘ACER Composite ADB Interface’ and select ‘Update Driver…’, in the opened window select ‘Browse my computer for driver software’ then ‘Let me pick from a list of device drivers on my computer’ in the list select ‘MTP USB Device’ and click on Next button.