If you are think of installing Windows 8 in Windows Virtual PC that Microsoft provides then all the best. In actual fact it cannot be done.
1. Download Oracle Virtual Box.
2. Set up a vhd disk
3. Mount the Windows 8 to the storage iso
If you start the VM now then you will fail to install Windows 8. Enable PAE/NX in System.
Do not open Windows Virtual Machine setting if you have one installed else let me know if your installation does not crash.