ODIN, RUU and Heimdall
For anyone unaware, ODIN is the Samsung equivalent of HTC’s RUU. Both are full ROMs which can only be installed via Windows. The ODIN ROMs can be used to restore a semi-bricked phone, that won’t boot to recovery or into the full OS, as all that is needed is Download mode. Download mode is simply accessed by unplugging the phone from the USB cable, holding the volume buttons and plugging in! There’s a more thorough guide on ODIN and Heimdall in the Basic Guides section of this website:(http://www.freeyourandroid.com/guide/building_roms_for_odin)
Heimdall is the Linux program to flash ROM. For information on Heimdall, click here.
Please be careful. Make sure to backup the existing ROM so that it may be restored before if it is bricked. One more caution, many ROMs offered and claimed to have been built from CyanogenMod are not working. It appears some unscrupulous developers launch HTC based ROM claiming it to be for some other phone and then judge from others experience as to what problem may arise.