I found this on http://www.i-hacked.com , I think that more than 1 may be interested.
In order to download the Bios Firmware you have to create a free account in I-Hacked.com
Warning - Do it at your own risk

Gastonl
www.gastonl.com



Canon EOS 300D Digital Rebel
Canon 10D Features on the Rebel?


When Canon introduced the Digital Rebel, the world's first entry-level Digital SLR camera, many remarked on its similarities to the 10D , its $500 more expensive big brother. In fact, the two cameras share much of the same technology and so Canon implemented a number of software-based limitations to avoid destroying sales of the professional-oriented 10D.

Now, a new hack that restores previously hidden menu along with a few additional tricks has added nearly all of those 10D features to the Rebel, with an arguably superior user interface to boot.

Instructions to update your firmware

BIOS FIRMWARE: E3kr111B71.rar
6/16/2004 - another beta ("B7.1"), minor fixes, no major additions.
- changeable MLU delay via C.Fn17
- right button mapping removed and now does nothing (normal)
- timer mode + MLU works normally now
- FEC1 displays on the LCD when changing the FEC
- AI OF (manual focus), AF OS (one shot), AF SE (AI servo) and AF AI (AI focus) shows on the LCD when changing the focussing mode
- the quick erase instead of hitting the Erase button twice, you now need to hit Erase then Set instead (this only applies during the quick review after taking a photo)

BIOS FIRMWARE: E3kr111B7.rar
New in this release:
- ISO 3200
- Mirror Lock up

Changes:
- FEC is moved to JUMP button
- 'Right' button has no function assigned
- 'Left' button selects the autofocus mode:
PA-1 - ONEShot
PA-2 - AIservo (dosn't work right now)
PA-3 - AIfocusAF
- the default button in delete prompt was changed from 'Cancel' to 'OK'. So, be aware. Now if you want to delete an image, press DEL button and then SET one. To Cancel press any other key.


------------------------------------------------------------------------------------------------------------------

Its been widely known that the Canon EOS 300D Digital Rebel and the Canon EOS 10D DSLR's are similar beasts. In fact, if you look at their side-by-side comparisons you can see that most of the features that vary are catagorized as "Customizable".

The 10D has a menu item called "Custom Functions" which allows these settings to be adjusted. Well, a fellow in Russia found that in the latest firmware, by switching a single byte in the firmware image, he was able to enable most of these 10D "Custom Functions" in the Digital Rebel. Now, some features, such as more frames in rapid shooting, are hardware-limitations but some features lacking such as Flash Exposure Compensation and embedded JPEG quality are found to be working in the 300D.

This is not the 10D firmware, it is the 300D firmware with some of the dormant 10D features enabled. The developers probably shared the codebase between the two models. The 10D firmware will not work on your 300D.

Now, be aware that this Modified firmware will violate your warranty!

The firmware is available here: Canon 300D Firware

The following data is from a long thread on DP Review's forums:

I have attempted to confirm what works, and if it does not specify ' [WORKS] ' then I have not confirmed it yet.

CF1: SET button func. when shooting. [WORKS]
0: Default (no function)
1: Change quality
2: Change parameters
3: Menu display
4: Image replay

CF2: Shutter release w/o CF card [WORKS]
0: Possible without CF card
1: Not possible

CF3: Flash Sync speed in Av mode [WORKS]
0: Auto
1: 1/200sec (fixed)

CF4: Shutter button / AE lock button

0: AF/AE Lock
1: AE Lock/AF
2: AF/AF lock, no AE lock
3 AE/AF, no lock

CF5: AF-Assist Beam / Flash firing [NO]

0: Emits/Fires
1: Does not emit/Fires
2: Only ext. flash emits/Fires
3: Emits/does not fire

CF6: Exposure level increments: [WORKS]
0: 1/2-stop
1: 1/3 stop

CF8: RAW+JPEG rec. [WORKS]
0:RAW+Small Normal
1:RAW+Small Fine
2:RAW+Medium Normal
3: RAW+Medium Fine
4:RAW+Large Normal
5:RAW+Large Fine

CF9: Bracket. sequence/auto cancel
0: 0,-,+/enable (300D default)
1: 0,-,+/disable
2: -,0,+/enable
3: -,0,+/disable

CF10: Superimposed display
0: on
1: off

CF11: Menu button display position
0: previous(top if powered off)
1: previous
2: top

CF12: mirror lockup [WORKS]
0: disable (300D default)
1: enable

CF14: Auto reduction of fill flash - not tested yet
0: enable (300D default)
1: disable

CF15: Shutter curtain sync [NO]
0: 1st curtain sync
1: 2nd curtain sync

CF16: Safety shift in av or tv
0: disable
1: enable

CF17: Lens af stop button function
0: af stop
1: af start
2: ae lock while metering
3: af point: m->auto/auto-ctr.
4: one shot -> <- ai servo
5: IS start


Savings: $500*

*If you're happy with the added features in this firmware, this is saving your $500 over the 10D...