There is an extended firmware exists for Canon EOS 300D cameras which can activate almost all of the extra features of the Canon EOS 10D.
The Canon EOS 300D camera is based on 10D: sensor with the same resolution, same LCD screen, compatible batteries, and even the size of the camera bodies are similar. But, the 10D is in an advanced DSLR, while the 300D is an entry level camera for beginners. In order to make those two cameras different, some custom settings were disabled in the firmware of 300D, which the 10D has. Fortunately, the disabled menu can be activated by a firmware upgrade, adding extra features to 300D cameras.
Some of the extras:
* ISO 3200
* custom function for SET button
* shooting without CF memory card
* flash sync setting in Av mode
* setting the quality of embedded JPEG in RAW
* mirror lock
Unfortunately some other extra features which is in the menu are not available, because some code was removed from the firmware. Furthermore, I have to mention that the interface language of the camera can not be changed when the extended firmware is installed. In order to change the language, the original firmware should be installed temporarily.
The extended firmware can be downloaded from here: http://satinfo.narod.ru/en/download.html
The developer's site can be found here: http://satinfo.narod.ru/en/index.html
The downloaded file should be extracted to the memory card, then insert it into the camera. It is highly recommended to charge the battery before the firmware update process. Then, update the camera's firmware. The new features can be found in the "Custom functions" submenu.