virtualbox.org

I download the latest VirtualBox 4.3.20 for Windows Hosts with x86/amd64 and tried to install CentOS7 64 bit ISO. The virtualbox only provide 32bit OS options. My computer is running 64bits Windows 7 OS. Why can I see 64bits OS option from the drop down list?

Thanks,
LearnLinux

From the FAQ: I have a 64bit host, but can't install 64bit guests.

Does anyone have an answer to this? Why can't I see the 64bits option on the VirtualBox? Is it because I am running Windows 7 64bits that it won't support it? I cannot find any posting related to this in this forum. Please help.

You have already been given a link to the FAQ, which certainly answers your question. What other help do you require?

I am having the same problems.

My setup is Windows 8.1 x64 bit host. CPU is i5-4460. I cannot see any options for 64bit guests.

And yes, I have made sure that virtualization IS ON in my BIOS and my cpu is CAPABLE. Hyper-V is uninstalled.

Had virtualbox 4.3.12 installed originally (which worked perfectly) and upgraded to 4.3.20. All 64 guests options are now gone. When I create a dummy vm, go into settings -> system, the acceleration tab is now disabled too. I tried reverting back to 4.3.12 hoping I could get 64 bit guests back, but now that doesn't work either. Not sure what is going on.

I installed my copy of vmware and everything is fine, virtualization and 64 bit guests work perfect.

Any help would be great!

There is nothing to add to what's in the FAQ. If you don't see 64bit guest's being offered then you have not fulfilled one of the items on the checklist - it's up to you to check each item thoroughly.

If you want to discuss this further then provide a VM log file, ideally for a VM in which you turned on VT-x. Right click the VM in the GUI. Select "Show Log". Save "VBox.log" to a file. Compress that file and attach it to a message here.

I posted this in the other thread, but my solution was to disable "Execution Prevention" in my BIOS. You might consider adding that as a solution in the FAQ.

No chance of that. The NX bit isn't relevant. Your true solution was probably that you did a full reboot of your PC when you changed the BIOS config. The need for the latter is covered in the FAQ.

and disable execution prevention indiscriminately is a security risk