since you are posting in the ATT forum,i assume that you have an att device.
sounds like you are simply not flashing a proper zip file,wich must contain,among other things,an android info text document,and if you are still s on,it must pass an htc signiture check,and have a relocked bootloader,if the file contains images other than boot,system,or recovery.
the sigiture fail error is becasue you are trying to use a file that has been modified,and no longer passes the htc signiture check.
a .exe file can be found at the link in this thread:
i just checked it,its leading you to htc's site,where the most current .exe file is availble.
you can get the utility to run by starting it with the phone in fastboot,or RUU mode( fastboot oem rebootRUU
). again,the bootloader must be locked if youre s on.
you can extract rom .zip in this manner:
the .exe utilities can be finicky,so if you have trouble getting it to run, you can extract "rom.zip" in the following manner:
-start the utility
-check the "i understand" box to move on to the next screen
-hide the utility temporarily out of site
-search your C drive for "rom.zip". you will find it in a temporary location(it will be in a different spot each time you run the utility)
-open the folder location,and transfer rom.zip to a safe location on your PC.
-unhide and cancel the utility,youre done with it.
-rom.zip can be renamed to PxxxIMG and flashed in hboot,from a FAT32 sd card
rom.zip can be flashed in this manner:
if youre working with a booted,operational phone,you can flsh the file in the following manner:
-open a cmd window
-change to adb/fastboot directory
(cd c:\mini-adb if youve used any of my guides )
-place the zip file you want to flash into adb/fastboot directory
-enable usb debug,disable fastboot,plug in phone
-check for connectivity
adb devices (should return serial number)
-boot to fastboot
adb reboot bootloader
-check for connectivity again
-flash the file
fastboot erase cache
fastboto oem rebootRUU (will put you in ruu mode,black screen silver htc letters)
fastboot flash zip zipfilename.zip (will send and flash the file. dont interupt it while the cmd window shows its writinging,and the green status bar is moving on the phone screen)
*sometimes a file will fail with a pre-update error. this is normal,just enter again:
fastboot flash zip zipfilename.zip
and this time it will finish
-when you get "finished" and "OK"
fastboot reboot-bootloader (takes you back to fastboot)
-reboot back to the OS
you can use this if you dont have an operational phone as well. you just need to manually put the phone in fastboot(select from hboot menu) then skip the "adb" commands and start with fastboot devices
be aware that the newest ruu will break the ability to achieve s off,so id be hesitant to do that if all possible.
is your phone currently not working? you should be able to install a rom,or restore a backup. some more info on your situation may help us help you