Win 10 64/ vb with ununtu 64 installed need 64bit vb on system

Question

I have win10 64 and using vb installed ubuntu 64 I want to install vb on ubuntu 64 but when I do I don't have 64 bit option on virtual box

Answer 1

For me it was the Hyper-V that was enabled (turn windows features on/off). I.e. you have to disable it (both can't work together as it seems).
Check this question/answer here:

Why does virtualbox only have 32-bit option, no 64-bit option on Windows 7?

If VirtualBox is only showing 32 bit versions in the Version list make sure:
Your Host OS is 64-bits
Intel Virtualization Technology and VT-d are both enabled in the BIOS
The Hyper-V platform is disabled in your Windows Feature list.

Also, more details as to 'why': Virtualbox has no 64-bit options

This is more of a summary (as Q/A on this are not that specific) and Hyper-V seems like the most common problem (virtualization is most often enable already, and you probably know what type of system you're running).

EDIT: this is not the answer to OP troubles, once he described what he actually wants, but I'm leaving it as it is for now.