No 64bits support after changing Guest OS

[vMo]

Hi Guys,

I was running Ubuntu 64Host on my DELL E6430 with a lot of virtualbox VMs, 32 and 64bits
Recently I had to reinstall my Dell with Windows 8.1 (64Bits) OS.
Since the host OS is Windows 8.1, I don't have any options to install 64Bits OS anymore !!
(only 32 bits OSs are listed)

Any ideas ?

Thanks
Vmo

[vMo]

I've found the answer by myself... for those who can meet the same issue...

Virtualbox and Hyper-V couldn't work at the same time on the same Machine.
You can find several ways to do turn off Hyper-V on your OS

Now, everything is working fine