BLU VIVO AIR had the same problem. I kept a blog about installing the general google usb driver to install here step by step and without funny links or ads - http://www.devfish.net/post/2015/07/20/android-usb-adb-drivers-for -blu-phones-vivo-air.aspx . Windows 8.1 ....
Use a USB cable to connect a Windows PC and a phone.
Open the device manager. You will see that BLU VIVO AIR appears in “Other Devices” as unavailable.
Download and install the Google Generic USB driver from http://developer.android.com/sdk/win-usb.html#top . Write down and remember the place where you install the Google driver.
Right-click BLU VIVO AIR, select Update Driver Software ...
Select "Browse driver software on your computer"
Go to where you installed the USB driver software for Google.
Select "Let me choose from the list of device drivers on my computer"
Select Show All Devices
Select "Have Disk"
Go to the place where you installed the Google USB driver, select the android_winusb.inf file
In the Driver Update window - VIVO AIR dialog box, select Android ADB Interface
Ignore the message "Update driver".
Now you will see the Android Device → Android ADB Interface in the device manager, and VIVO AIR will disappear from the "Other devices". Now you can also enable features such as USB / Mass Storage Mode so you can view files from Windows Explorer and debug your device.
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