Or download the carbon cloner and clone you're startup hd to the other HD .
Be sure what you select the source and destination drive correctly
To be sure after cloning restart you're computer while you hold the Option key down
Chose the clone Hd to start up .
If it is OK , go to System Preference and make the clone you're startup HD
My point is that you can only install from a newer version retail DVD - which may not exist.
Your Mac came with 10.6.4 - you need a retail DVD with 10.6.5 or newer. (Sorry, I don't think that exists.)
So, it appears the driver(s) or other support files are unique on your mini.
Is there some reason you don't want the server features?