How to edit a OS ROM?

[FSY]

I'm use a HTC64 Extended ROM Tool to decode a ROM already, but how to edit a ROM on next step? I use a prepare_imgfs.exe and viewimgfs.exe but have a same problem...

[nuclear]

I'm use a HTC64 Extended ROM Tool to decode a ROM already, but how to edit a ROM on next step? I use a prepare_imgfs.exe and viewimgfs.exe but have a same problem...
If i find a windows crossbow ROM for Hermes, how can i modify it to work on the Universal? If i find a windows crossbow ROM in another language how can i change it to english?
Can the above tool be used to do this?

[mamaich]

http://forum.xda-developers.com/showthread.php?t=249836