As I recently posted, I also changed my boot screen on my HTC Desire, this is the second screen that comes up when you turn on the phone and is normally animated.
With the Telstra HTC Desire, the normal methods of putting a “bootanimation.zip” file into /system/media never worked for me, even after I rooted the phone.
I found out that the Telstra HTC Desire has a file in /system/customize/CID called default.xml which contains a set of lines starting with
Removing those lines from the default.xml file will allow you to put the “Bootanimation.zip” file into /system/media and the android_audio.mp3 file into the same location.
Once the files have been placed there, you will now get the new bootanimation instead of the Telstra boot animation.