I Have Dell OPTIPLEX 755 machine with VT enabled in BIOS but when i trying to check using KVM i am getting following error

I am missing something?

root@nova-controller:~# kvm-ok
INFO: /dev/kvm does not exist
HINT:   sudo modprobe kvm_intel
INFO: Your CPU supports KVM extensions
INFO: KVM (vmx) is disabled by your BIOS
HINT: Enter your BIOS setup and enable Virtualization Technology (VT),
      and then hard poweroff/poweron your system
KVM acceleration can NOT be used
root@nova-controller:~#

UPDATE:

root@nova-controller:~# sudo modprobe kvm_intel
FATAL: Error inserting kvm_intel (/lib/modules/3.2.0-26-generic/kernel/arch/x86/kvm/kvm-intel.ko): Operation not supported

dmesg

[   57.887352] kvm: disable TXT in the BIOS or activate TXT before enabling KVM
[   57.887354] kvm: disabled by bios
[   61.199353] kvm: disable TXT in the BIOS or activate TXT before enabling KVM
[   61.199355] kvm: disabled by bios
[  965.566334] kvm: disable TXT in the BIOS or activate TXT before enabling KVM
[  965.566337] kvm: disabled by bios

In your BIOS you should have the following settings:

• Security: Execute Disable should be On
• Performance: Virtualization should be On
• Performance: VT for Direct I/O Access should be On
• Performance: Trusted Execution should be Off

After changing these and saving the settings, physically power off the computer and power it back on.