unable to sync Dell Inspiron 15 5000 model 5558 with itunes

I had the same issue a while back. Here's my little guide on how to fix it (If you are on Windows 7 or 8 it may look a little different). On your home screen click the Windows Icon on the bottom left corner

on the bottom there should be a search bar

type in drivers and click where my mouse is hovering

Then a program will open up and have a list

click on each of the bulletpoints and more options will come up

right click on the first one and this will appear

click "Update Driver Software" then this will pop up

then select "Search automatically for updated driver software" and then it will look online for new drivers and install them as shown here

just wait for a few seconds or minutes then repeat on each item there

Your cable might not be good. You should get an apple cable for your devices. using any other cable that isnt at least apple certified can reduce your total phone life and it might not work properly with your devices.