Put the phone in Update/Recovery mode (turn it off, press and hold the Camera button, turn it on again, keep holding the Camera button until it goes to the black-and-white screen indicating that you should connect the phone to the PC). Connect your phone to the PC using the normal USB cable. Start the Zune software. After a few seconds, Zune should offer to restore your phone to the backup that was created prior to beginning to flash the update.
That will make the phone boot again, without losing any data. Afterward, you can try updating again. Hope that helps, good luck!
Win8/Windows RT projects:
List of desktop apps for hacked RT devices
Native Access WebServer and Libraries
WP8 Interop Unlocks
Storage Cleanup tool
XapHandler, Root Webserver, OEM Marketplace XAPs, Bookmarklets collection (Find On Page), Interop-unlock hacks.
Do not private message me with questions that should have been posted on the forum!
Not only are you wasting your time - I'm not going to bother writing an answer to such a question for only one person - but I will probably block you from PMing me in the future as well.