That was the same problem I had.  To solve it I de-installed the VM Virtualbox rebooted and went into the BIOS then checked my CPU settings.  I had to enable processor support for VM's in the BIOS CPU configuration.  Saves the change booted up then reinstalled VM Virtualbox.

That's when I could choose the 64 bit Win 8.1 in the VM Drop down.

I'll give it a shot. Thanks

I burned a disk and just went for it on a full install to my main drive. I did of course back up all of my documents and such to an external drive just in case. But I have to tell you that I'm very pleased so far with how everything is going. Speed wise , things are pretty snappy. I'm using WindowBlinds 8 , Start8 , and Iconpackager, and so far ,everything is performing without a hitch !!!   I'm very impressed so far. I also love the fact that you can pin almost everything to the taskbar ( including hard Drives and externals) without jumping through hoops. Very, very nice so far.          -- Ace --

I went into the BIOS setup and there was no CPU configuration. Just the usual...main...power management...boot...etc etc. I get that same screen and it says its creating a process but does it have to take hours? I'm really getting fed up! It just keeps hanging.

BTW: I thought it was supposed to be for both 32 and 64 bit yet it lists only 32 bit. I think I said that. Anyway...I uninstalled Virtual Box. Gonna try to re-install and see what happens. Where's the duck when ya need him. 

Uvah....dunno what it is that you're getting...unless it's to do with the difference between a dynamic disk and 'formatting' a fixed size one...

My VB ver is 4.3.6 ....the current is 4.3.12 and from memory I used the 32bit of 10.

Full install took only a few minutes....there was no hang...

I got the 4.3.6 version of VB and the 64 bit Win 10. Should I go for the 4.3.12 version then dl the 32 bit W10? During the install I did the dynamic disk. Dunno if that's the problem though. I haven't re-installed VB yet, hoping for some kind of solution.

No need to go to 4.3.12 ...as I am fine with the older ver....and used 'dynamic'.  Read somewhere that 32bit was the one to try....[or maybe it was me being lazy/conservative with dl size....the 64 is a bigger iso...and I have a monthly dl limit].

Did you google the error?

Didn't google as the error is the screenie I put up. There was no error code. I'm downloading the 32 bit version now. We'll see how that goes.

It doesn't matter re a 'code'...you google the text message....

Here's a hit...

https://forums.virtualbox.org/viewtopic.php?f=6&t=63755 

Solution....possibly....disable your AV prior to starting the VB proggy...and running the 'machine' ...

Link's problem was re host having 'Avast' as its AV ...

I have very little trouble with VMWare, I find it much easier to use than VirtualBox. But it doesn't have a free version, only a trial.

Ok...re-installed VB. Deleted the 64 bit preview. Have to wait on dl'ing 32 bit version. Tried last night and got as far as 1.2 gigs then a popup says windows detected another computer on this network with the same IP address, download failed. Gonna keep at it. I'll let ya know. 

Un installed Avast and installed Avira in its place. Went to PCmag website to check out different free AV's and Avira was their top choice. Anyway...I dl'd the 32 version Win 10 and it seemed to install correctly but when I hit start it starts creating the process and hangs. Its still doin' it even now, an hour later.  

When you setup VM you need to make sure you have the right internet setting  established.  Try either NAT or Bridge.  Bridge worked for me. 

Also look at the advanced setting there and make sure it doesn't day Deny(it's the default).  I set mine for all.

It caused so many problems. For one I couldn't shutdown the laptop, wouldn't reboot, couldn't kill the processes or the .exe. Always getting access denied. Found a way to finally get rid of Avast AND bitdefender leftovers by deleting them in safe mode after going into msconfig and stopping processes there. For now its uninstalled until I clean up the HD. Too much on it and not enough room for other stuff. Hopefully after that.

I have a question:

What Stardock Apps should I install on my Win 10 Tech Preview??

So far I've tried Object Dock 2.

Suggestions?  Have you tried it first?