There is no default username/password for SS4200-E. It is set during the first time setup, and if you lost it yes you'll need to reset your system. Also take note that you need to press and hold the reset button for ~5 seconds to reset system defaults. See http://www.intel.com/support/motherboards/server/ss4200-e/sb/CS-028587.htm for details.
After enough reboots/resets, it eventually prompted me to create an admin account. Unfortunately, the first thing I tried to do with this access was to change it to a RAID10 config. The disk prep started, but never got past 0%, so now I have a steady amber power light & cannot access, nor reset, my ss4200e. If anyone has any advice on recovering from this state, it would be much appreciated--thanks!