My iPhone 4S won't let me install iOS 5.1?

Alright, so I tried installing the update both on my iPhone and laptop and both didn't work… Like, it downloads but then when it's like 30% it just stops and gives me this error that the installation couldn't be completed. On my iPhone it shows a window that says " Error downloading iOS 5.1"…

I also faced this problem with my old iPhone 4… And I've tried using different Wi-Fi connections (at my friend's, at home, at work… )

What could be the cause of such a problem?

Any help would be highly appreciated.

Note: MY PHONE IS NOT JAILBROKEN.

You may find an answer on Apple support page. I put the link below addressing your issue for you to look at.

  • Why won't any cracked apps install on ios 7 with appsync 7.0+? I have a jailbroken iPhone 5 running ios 7.0.4. I downloaded appsyn 7.0+ from cydia, yet it still keeps failing to download any cracked apps. I've tried using appcake, zeusmos, and i-funbox yet none are installing.
  • Why won't my iPhone 4s let me update my software to IOS 6? I've tried everything to try to get it to update! It's really starting to piss me off to the point of wanting to get rid of my phone and going back to my old android phone! Anything that may help is appreciated. I have 3gb available, so that isn't the problem. It says it's installing, then an error message pops up.
  • Why won't it let me install ios 6? I want to install ios 6 but it is saying i need atleast 2.5 gigs of storage space. I have 3.8 gigs of storage available in icloud and i barely have 8 gigs of stuff on my iphone 4s 16 gig.
  • Why won't iOS 8 install on my iPhone 4s? Been trying to install the update all week and it keeps getting to almost 100% installed and downloaded and then it says it can't install IOS 8. I can't find a reason as to why it won't install, any advice?