Last edited by strollin; 28 Nov 2013 at 15:11.
The plot thickens.
I just attempted to upgrade another one of my VirtualBox Win 8 VMs to 8.1 via the Store and got the same message as the OP, "not supported by your CPU". I have upgraded several in the past without issue. This VM runs on an i7-3770K cpu.
I tried adding PAE/NX support but that had no effect. I downloaded and installed the latest version of VB (4.3.2) which didn't help. I then ran the Win 8.1 Upgrade Assistant which told me that I couldn't install because my cpu lacked support for CompareExchange128.
I have an ISO of 8.1 so attempted an upgrade using the ISO and got the same message. However, I created a new VM and used the 8.1 ISO to do a clean install and it installed and runs fine in a new VM. Not sure why the upgrade fails while a clean install works fine.
I searched and found links detailing how to get around this issue with the preview: VirtualBox CompareExchange128 Error on Windows 8.1 Preview Install but that was of no help and supposedly, newer versions of VB solve the issue.
I also downloaded and ran an MS utility called CoreInfo which details all the info about your cpu and it reports that the cpu supports all of the required cpu capabilities.
So far I have not been able to figure out why this particular VM won't upgrade while others upgraded fine. Hope this info proves useful to others.
At the moment, I'm thinking it is a bug with VB.
If you're on version 4.3 that might be expected. Several of my VM's crashed without modifying any settings. Machines were running on VBox 4.2 without issues, then suddenly crashed on 4.3, even the VM additions were updated but wouldn't help it. I suspect this to be related to the new VT-x code that runs in 4.3 and I do believe there are some bugs to solve, especially on W8.1.
Strollin, will your license key work with the Windows 8.1 full install? I only have an Windows 8 license key, so I went the upgrade route and am hesitant to do a full install.
Stay tuned because 4.3.4 will be available soon, folder exists already. We'll see if some fixes were applied regarding Win8.
You guys should test that out when possible. But in any case I wouldn't recommend upgrading any OS in a VM, but for testing only, since a clean install will always be faster. During the upgrade, the OS requirements change and unless you adapt the VM settings between shutdowns some major requirements will block you. THE OS UPGRADE ISSUE IS NORMAL FOR VM's.
If you upgrade an OS in a VM then the first thing you do is Change the OS version form the settings and reinstall/update the VM additions. But we've already did this step to begin with, right?
Of course this might not always fix it if some bugs exist for the particular case.
Hopachi, I upgraded to VirtualBox 4.3.4 and switched the VirtualBox guest operating system setting to Windows 8.1 and booted Windows 8. There were no complaints about the mis-match. I proceeded to Windows Store and this time the upgrade to Windows 8.1 was permitted.
I don't know if the switch to VirtualBox 4.3.4 was the reason for the success or if it was the VirtualBox setting for the guest operating system. (I believe that in the past, I tried the guest system selection change and it did not help so I went back to selecting Windows 8 just to be consistent with the guest system that was actually being booted.)
There were some Windows guests and host changes included, a bit more fixes than 4.3.2 brought.
After reading of how you said you switched the guest OS setting to Windows 8.1, I was skeptical since I thought that setting was only taken into account when first creating the VM. I was pleasantly surprised when I was then able to proceed with the upgrade. I've never changed that setting on a VM once it was already created.