Getting stuck at DMI generally means things along the lines of the master boot record or Bios is somehow corrupted, or that bootable devices are either not set properly, have loose connections, or are failing. In this case it sounds like perhaps your Optical Drive might be the issue.
Yah - The 'normal' boot sequence is Optical first, since there could be occasions when you don't want to boot from the HDD. Having said that, you can have the sequence in whatever order you want.
How to perform a Startup repair:http://www.vistax64.com/tutorials/91467-startup-repair.html
Some other things you might find useful:
How to check system files in Vista:http://www.vistax64.com/tutorials/66978-system-files-sfc-command.html
How to perform a full system repair:http://www.vistax64.com/tutorials/88236-repair-install-vista.html
Hope that helps.