before install Windows 8, I wanna how long it will take?

half an hour?

one hour?

What if the power off when I am installing Windows 8?

Because I am the company IT consultant, I need to take full responsibility about the system re-installation.

It takes appr. the same amount of time it took to install Windows 7, and if you have a power interruption, the install will pick up where it left off at. And WTF if you are a IT Consultant are YOU putting WDP onto production machines for? I suggest that if you like, and want to keep that job, you go into the network farm, grab a couple of machines ask the company IT department to give you a separate network partition, and IP Addresses so that you can test the company applications to make sure they will work in WDP, which I assume is the reason you want to find out this information. NOTE: with old machines expect it to take awhile longer to install, due to their slower processor(s), and the amount of RAM installed in them already.