I had the same problem and I solved it by following these steps:
- Press the WINDOWS + X.
- Choose "Programs and Resources" from the list.
- A window will appear, click on "Enable or Disable Windows Resources"
- From the list that will appear, UNCHECK the Hyper-V folder, click OK.
The hyper-v must be disabled in order to install HAXM.
Maybe you should reboot before trying to install it again.