FYI: I have an Acer Aspire ES1-111M, Windows 8.1, 64 Bit, brand new. On 5-15-15 I installed an optional Windows Update "Intel Corporation - Other hardware - Intel(R) Serial IO I2C ES Controller". This update disabled the laptop's mousepad, but the external mouse worked OK. I was not able to uninstall the update with the regular Windows Update program. I opened Device Manager, expanded System Devices, and found "Intel(R) Serial IO I2C ES Controller". I right clicked the driver, clicked properties, went to the Driver tab, and clicked Roll Back Driver. After restart, the mousepad works again. Maybe this information can help somebody else out there.