iphone 5 ios 7.1 update problems

In reply of the help extended by Ethmoid : I use microsoft windows os for itunes. My wi-fi, 2G/3G internet on the iphone just wont connect !

Regarding the question asked by Rojmer : The entire process of "Extracting software", "Preparing iphone for update" appears on my itunes. And then suddenly this error dialog box appears << " The iphone could not be update. An unknown error (3004) occured. " I have tried all those suggestions that have been made on the Apple's site to correct this error. But it didnt work out ! PLEASE PLEASE HELP !!!!!! 😟