LBPHeretic
Android Expert
Has this handset ever been updated before with the stock Android 2.1 RUU? I think the bootloader, also known as HBOOT, gets updated from version 1.41 to version 1.47 with the Android 2.1 RUU and that prevents the installation of the old Android 1.5 RUU.
I did a little reading and have seen some suggestions to remedy the issues with the flashable Android 2.1 RUU .zip file. People have copied the contents of their microSD card to their computer, formatted the microSD card, and then copied the files back to it from the computer. After that, they try the flashable Android 2.1 RUU .zip file again and it works. Another suggestion was to make sure that the zip file is in all caps. So, you would want it to be "HERCIMG.ZIP" and not "HERCIMG.zip" so give that a try too. I still do not believe it matters if you are on HBOOT version 1.41 or HBOOT version 1.47 to use the flashable Android 2.1 RUU .zip file, but anyone that has updated to Android 2.1 officially in the past should be up to HBOOT version 1.47 anyway, so it should work.
I did a little reading and have seen some suggestions to remedy the issues with the flashable Android 2.1 RUU .zip file. People have copied the contents of their microSD card to their computer, formatted the microSD card, and then copied the files back to it from the computer. After that, they try the flashable Android 2.1 RUU .zip file again and it works. Another suggestion was to make sure that the zip file is in all caps. So, you would want it to be "HERCIMG.ZIP" and not "HERCIMG.zip" so give that a try too. I still do not believe it matters if you are on HBOOT version 1.41 or HBOOT version 1.47 to use the flashable Android 2.1 RUU .zip file, but anyone that has updated to Android 2.1 officially in the past should be up to HBOOT version 1.47 anyway, so it should work.