Hyper-V (comes with windows 8)
First you have to add Hyper-V to your Windows 8 installation. In explorer, go to add/uninstall programs. on the left is: Windows features activate. There you check the Hyper-V. easy.
Now on the start page, you will find 'Hyper-V manager'. Make a link to desktop or start for easy use.
In Hyper-V, create a virtual machine. use the type 1 (no secure boot). Remove the netcard and the SCSI component from the new virtual PC. Add a virtual disk 'hdd1.vdh' with 1GB and MBR-partition style. Do not use .vdhx.
Important: In the virtual disk don't create a volume or drive letter, yet. Don't format it yet. Add the reactos-install-iso as cd/dvd image to the VM.
Start the VM .. It should boot from the install cd. You should see the light blue background. In the installer you create a big partition and format it with FAT. let the installer install a bootloader in VBR, not in MBR. Installation is fast. Reboot from disk and enjoy. ReactOS will find a ACPI device but not a driver. Just click it away. When you shutdown the VM you can mount/unmount the virtual disk in your windows 8 explorer. With right click and the hdd1.vdh. now you can copy/rename/delete files in your reactos installation.
The Hyper-V also allows kernel debugging. You create a pipe for the virtual com port. It is the same like kernel debugging of a normal windows-VM. Google kernel debugging with hyper-V.