Every time I re-install Windows and the QT client, I have to re-download the entire block chain which takes a long time. Can I copy my existing block chain files so that I won't have to re-download the same parts over and over each time? If so, is there a tutorial on the subject, or is it just a matter of moving files in and out of the installed directory, eg. C:\Users\USERNAME\AppData\Roaming\Bitcoin?
Yes you can copy blockchain from that appdata folder and then copy it back there again.