This is the wrong forum, but I am sure this will get moved. When moving to a new setup I usually do a fresh install of windows and then use the HDDs in the computer or enclosure and copy the data.
I usually partition my drives so that my OS is on one partition and I use the other as the storage. My games (now) get installed on my raid. So I don't have to copy that. So all I have to do is install the OS.