Hi I have this board DP55WG and recently I have reassembled it into another case. Issue arises when I can only boot to BIOS with "System is booted in Back2BIOS mode" but the B2B switch is indeed turned off, I have tried too many solution but to no avail.
Would destroying the the switch help? Or do I downgrade BIOS to an older version?
Sometimes, the B2B button will catch on the I/O Shield and not disengage completely. Play with it; you should be able to get it to the right state...
Hope this helps,
I am following your case; let me know if you were able to fix the issue.
This workaround might help you, change the position of the BIOS jumper, turn the B2B off and power the board up.