Maybe VT-X is not enabled in your BIOS.
See Intel HAXM documentation here: http://software.intel.com/en-us/articles/installation-instructions-for-intel-hardware-accelerated-execution-manager-windows
Intel VT-x not enabled
In some cases, Intel VT-x may be disabled in the system BIOS and must be enabled within the BIOS setup utility. To access the BIOS setup utility, a key must be pressed during the computer’s boot sequence. This key is dependent on which BIOS is used but it is typically the F2, Delete, or Esc key. Within the BIOS setup utility, Intel VT may be identified by the terms "VT", "Virtualization Technology", or "VT-d." Make sure to enable all of the Virtualization features.