If your processor does not support Virtualization Technology then you can't run Windows 8 in Virtual Box....you will get a black screen of death. In order to find out if your CPU supports hardware Virtualization Technology you can download the Intel Processor Identification Utility here http://www.intel.com/p/en_US/support/highlights/processors/toolspiu/
if it is enabled then you need to turn it on in your BIOS, to see how to configure BIOS, go to this page http://www.microsoft.com/windows/virtual-pc/support/configure-bios.aspx
After BIOS has been configured, you need to do a reboot, shut down, wait about 10 seconds and then start up again.
Now you are all set...have fun