First off, I'd suggest creating a new boot configuration mimicking your original and make sure to type in the password, even if it appears to be there when you get to that screen. I've seen issues where the password file (.acl) gets corrupted somehow and no longer works.
For pulling the image from a flash drive, make your image file a self-extracting .EXE. Then set up your flash drive as bootable (a number of ways exist to do this - you could create it as a network boot disk, for example). Then copy the image file to the flash drive and then just execute the image file from the flash drive.
HTH!