real quick - if you are unlocked but not rooted - you can dl clockwork mod custom recovery and place in the same folder as your fastboot.exe file. also download the 4.04 update to your sd card.
then you boot the phone into fastboot (with usb debugging checked, make sure you have lots of battery and DO NOT DISCONNECT DURING THE PROCESS of all this), open up the command prompt/terminal window, and do the following:
Code:
fastboot boot recovery name-of-recovery-file.img
this will boot clockwork on your phone, where you can make a nandroid backup (to be safe), then wipe cache partition and dalvik cache, then install the 4.04 update .zip and reboot the phone when it's done.