The IGEL M300C has a standard PC Phoenix Award BIOS - hit the DEL key repeatedly on power-up in order get into the BIOS setup screens.
In the dmesg output we find: IGEL Technology GmbH M300C/CN700-8237, BIOS 6.00 PG 08/19/2008
The BIOS boot options are:
Booting Puppy Linux from a USB connected CDROM drive worked well. The on-board Compact Flash card is visible (sda) and contains a single Linux partition (sda1), however I'm not sure exactly what filing system is in use as Puppy would not mount it. (ie It is definitely not ext2 or ext3).
The unit was set up for a screen resolution that doesn't quite work with my monitor so I've had little opportunity to see what it does as standard. I did manage to click on the right menu item to get into setup, but the first thing it wants is an administrator password....
Further research shows that you can bring up a boot option screen by pressing the ESC key as the system boots. What you get presented with is:
This looks quite promising. Unfortunately it isn't the case. For Emergency Boot the Igel manual says:
If you choose Emergency Boot (setup only with standard parameter values), the secondary stage loader looks for a bootable system in the flash and continues the boot process as in the other boot modes. Emergency Boot basically starts the X Server without the network driver at a resolution of 640x480 - 60 Hz and finally starts directly into the setup. This is very useful if you selected a too high screen resolution or configured a wrong mouse type.
What it omits to tell you is that first thing that happens is that you get prompted for the administrator password. Without it you can't change anything. A new system comes with no password set. If you find you have one then that has been chosen by the previous owner - there is no default that might work.
Reset to factory defaults is equally as bad:
...If the terminal is protected by an administrator password, you will be prompted to enter this. In case this password is not known anymore, you will have to contact us by using the online support form on our web page www.igel.com in the "service" section. Provide the displayed terminal key and the stated firmware version and, of course, your contact data. The terminal key will be displayed after pressing Enter three times. Our support will provide a so-called reset to factory defaults key for this specific unit. (Every key is valid for one single unit only, to keep this process at its most convenient, but still secure.)
I did try removing the Compact Flash card and connecting it up to another Linux system. I couldn't mount the file system. Searching the content revealed the following text in the loader:
The root/system partition is not of type CROMDISK
...which I assume is some Igel-unique form of Compressed ROMDISK. So there's no easy way to clobber the password files and get rid of the administrator password.