Out of curiosity I decided to try to install Windows 10 Technical Preview on Oracle VirtualBox and after several failed attempts I managed to get it going...
As Microsoft is currently building Windows 10 and it's still early I would not recommend using it as your main operating system. Below is how I managed to do it...
1. Getting started Make sure VirtualBox is up to date... this will solve most if not all problems! Grab the ISO from here
2. Creating the Virtual Machine
First off open VirtualBox and click on New in the manager window.
In the Create Virtual Machine pop up use Windows 10 as the name (Or anything you prefer), then select Windows 8.1 (32bit) or Windows 8.1 (64bit) depending on your version then click next.
On the Memory Size page just click next as 2048 MB (2 GB) is fine, and again just click Next on the Hard Drive page on the Hard Drive Type page again click Next as VDI (VirtualBox Disk Image) is fine, the next page Storage On Physical Hard Drive is your choice I personally choose Dynamically Allocated as I only want to use the space needed, however Fixed Size is slightly faster, on the final page File Location And Size choose where you want the file to be located on your computer and the amount of disk space you want to allocate to the virtual machine, then just click Create.
Once the virtual machine has been built click on the Start button in the manager, then in the Select Start-up Disk window, choose the Windows 10 ISO you downloaded early (Click the folder icon and choose the file), once that's done click start then the virtual machine should begin to load.
Once it has begun loading it will ask you to choose your language, once done click on the Install Now button and choose Custom: Install Windows only (advanced) option.
Click Next and the installation will begin rebooting as it needs to.
When it’s done, you’ll be given the option of using express settings, or customizing things. It’s easiest to select the first one.
Sign in with your Microsoft account (entering a code as required), and then finalize everything else.
It will start at the desktop, and one of the first things you’ll see is a Welcome to Tech Preview icon.
Click this and an Internet Explorer window will open with tips and tricks, access to the technical preview forums and more.
If you want to resize the OS window, click View in VirtualBox and select Fullscreen or Scaled Mode.
The simplest way to shut down Windows 10 when you no longer need it is to click the X in top right corner of VirtualBox and select "Power off the machine".
If VirtualBox encounters errors and fails to install Windows 10, the first thing to do is make sure you’re running the very latest version of the virtualization software.
If that doesn’t fix the issue, go to System Properties on the host (not the virtual) PC, click the Advanced tab and click Settings under Performance.
Select the Data Execution Prevention tab and change the setting from Turn on DEP for essential Windows programs and services only to Turn on DEP for all programs and services except those I select.
OK that, restart your system and this time Windows 10 should install just fine in VirtualBox.