Create a new ISO image file
If you placed the files in D:\Windows8ISO, you can use the command line below, otherwise you have to adjust the folder names so they correspond to the location where you saved the files.
oscdimg -lWin8 -m -u2 -bD:\Windows8ISO\boot\etfsboot.com D:\Windows8ISO D:\W8.iso
Here is a brief explanation of the commands. Behind -I you have the label of the disk, Win8 in this case. -m indicates that it will create a DVD image (larger than a CR-ROM). -u2 gives the DVD a UDF file system. -b refers to the boot image, and the last one is the actual name of the ISO file.
After pressing Enter you will have created an ISO file that can be used in Hyper-V and VMWare or to create an installation DVD or stick with. Below you can see the dialogue window where you are asked which version of Windows you'd like to install. When it asks you to enter a serial number, you can skip that step.