Bootloader - how (unsolved yet)

Beeing used to the community with my HTC devices - it seems that we are at loss currently to have low-level access without the operating system running. The only thing that runs well are the itsutil tools from XDA devloper "itsme" - look there: http://wiki.xda-developers.com/index.php?pagename=XdaUtils
Also other tools that operate on the extracted filesystem images (e.g."ROM Kitchen" or also WM5editrom) are working as expected - yet I did not dare yet to flash back anything via pdocwrite :-)

Some low-level acess should be possible, however I do not yet know how. What I found out so far is:

• Pressing power-on and holding the message-key will send a USB signal to a connected PC. The Windows-XP PC then searches for a "Neptune" USB device - for which the web hardly offers anything useful, except:
• The Motorola Flash tools (yes another deja vu with Motorola) require dedicated drivers to install. After this is done succesfully - well nothing more happens.

It seems that in the very short time (3 seconds) that this temporary state of USB exists some communication has to be established to keep it alive. Any hints are welcome.

I have also hoped that tools available for the BenQ P51 may help here, but it just seems that they are not doing more than itsutils can do already. And since we do not know yet addresses of the various parts of the ROM, nothing gained here either :-(