If you tried to install Windows 8 in VirtualBox, you saw that you could not complete the setup due to various errors.

If you want to install it you have to create a new virtual machine like this:

1. Make sure that your CPU supports the VT virtualization extensions
2. Create a new Windows 7 VM for 32bit
3. Give it more than 1GB RAM
4. After the creation, go in settings
5. In System, in the first tab, enable IO APIC (VirtualBox suggests to don't enable it for Windows systems, but we will enable it anyway)
6. In the second tab, enable PAE/NX
7. In the third tab, enable VT-X/AMD-V and the nested paging

Now the setup will be successful

After the setup, you might want to increase the screen resolution to run any Metro application.

If you want to disable the tablet interface, you can follow this other guide.