virtualbox.org

Hi,

I've installed VBox latest version in Windows Server 2012 virtual machine but when I start the application it's allow only 32-bit, I know changing the virtualization in the BIOS configuration in physical machine will fix the issue but this in virtual.

I tried also windows 10 virtual also same.

please help.

You seem to be describing nested virtualization, which is only supported in narrow circumstances. You have not described any circumstances: host VM platform (only latest VirtualBox is supported), VirtualBox version (host and guest), precise CPU model, and whether "nested VT-x/AMD-v" is enabled in VM settings|System|Processor.

Also, a zipped VM log should always be provided when asking such questions: it would save a lot of time.