Step 1 AND THIS IS THE MOST IMPORTANT out of all of them...and I don't mean to be an ass here, but ATT Titans are having a LOT of problems with getting the HSPL on their devices.
Everybody STOP!!! Take a deep breath! Exhale! You need to be more specific and explain to us what exactly are you trying to do. It's February 4th and we're post-release of Microsoft/carrier of their official "stock" Windows Phone 7.8. Is your phone HSPL or not? Your message indicates you're using WP7.5.7720 which is somewhat old given there have been at least 4 incremental updates since 7720 - 7740, 8107, 8112 and 8773 and a few on AT&T, 8779. I am not aware you can jump from 7720 directly to 8858 without going through the other increments; now you can do them individually or set up Cab Sender to them in order if that is your method of madness. You do not need HSPL to do this now. If you're HSPL we're not updating via Zune or Cab Sender; you're flashing in bootloader mode and there isn't an easier method, getting HSPL, is a crap shoot but if you have it, updating is cake. Let's start with what exactly are you trying to do, what is your bootloader SPL, and what is your build...
