iTunes iPhone Update Error Code 45
Take a look at The iPhone Wiki's website where it states that Error 45 is:


  Same with Error 6, in terms of resizing partition issue. But this may occur at the very beginning of restore process.



Whereas on Error 6 they write:


  
  Not enter the downgrading mode, change USB port (the back one of chassis is better) and restart computer.
  Unable to resize partition due to full storage problem at final stage of updating firmware. The error may be bypassed (restart and do exit recovery) but you probably need to re-update it one more time.