shark,
Unfortunately, you can not flash a new bios without a method of bypassing your current bios.
This means you WILL need a passme2 device, authentic ds game, and your current flash card.
order a passme2, and specify which game you have:
http://www.dspassme.com/oscommerce/catalog/product_info.php?products_id=52&osCsid=bdc8648acffdd0b8cbe0510a0651f520write this file to your flash cart:
http://www.ndshb.com/cgi-bin/cfiles/cfiles.cgi?0,1,0,0,10,74(yes it is version 6 of the bios, but it is the easiest option, you can upgrade to version 7 later)
put your game into the passme2, put the passme2 into the ds, put the flash cart into the ds. turn it on. Select the game you have inserted into the passme2. reboot, the firmware patch should come up automatically. Flash it properly this time. You can decide if you would like to upgrade to 7, just remember, that you will need to short sl1 when you upgrade to 7.
I have a red '05 ds. this is the procedure that I used.