Having trouble restoring backup of my iPhone

Having trouble restoring backup of my iPhone

I'd been having a few issues with my iPhone 4 (one of the main being that
apps wouldn't open and turning it off and on again to remedy this resulted
in me losing all of my contacts in my address book). When attempting to
restore my iPhone, it sometimes causes my computer screen to become
distorted and freeze my computer.
I'd been on iOS 5.1 (?) for a while (having put of updating it due to lack
of space) and my brother suggested updating to the most recent iOS. I did
this, but afterwards, my phone said it had to reset back to factory
settings. I reset it, but when I went to restore my backup, I got the
message "iTunes could not restore the iPod 'NAME' because the backup could
not be saved on the computer." Having looked around, people seemed to
suggest that I needed to clear some disk space on my laptop. I've done
this, and I have 217 GB free, so I can't see why this should be an issue
now, but I'm still having the same problem.
Can anyone suggest a solution?