Finding corrupt files on my computer?

So I'm having problem with my iPhone 6 app playing music. It plays at the most 1 or two songs and crashes. Most the time it crashes immediately upon opening. I have tried everything for a simple non techie would do. I even took it to the Apple store for help. They and online told me I have corrupt music files on my computer but the same music plays just fine on my MacBook and my iPod Nano.

Itunes will not import music without having to delete all my previous ones?

Itunes will not import music without having to delete all my previous ones?

Added (1). I have previously used my Itunes to import music onto my iphone 6, but currently when I connect it the program recognizes my phone but will not let me sync music without deleting all my songs first. I'm on the same computer btw.

Why is my Iphone 5 constantly saying storage almost full?

I have a Iphone 5 that was 16GB of memory.
I do not use itunes and recently I keep getting a reminder saying my storage is almost full, and it won't let me take a mere photo without having to delete 20 beforehand.
I have deleted around 8 apps, old messages, over 1000 photos, and I'm still getting this message.
I have looked online and someone said about backing up your phone on itunes on desktop, then restoring it, as it makes copies so would take up less memory.
Can anyone offer some advice on this?

How to connect my iPhone to iTunes? - 1

Okay so I just ha my iPhone unlocked via eBay and today the seller told me that to complete the unlock I have to put a new SIM card in my phone then connect my iPhone to iTunes via the USB cable, how do i do this? I haven't got any kind of iTunes program downloaded to my computer, so how do I do that? Do I have to download it or can I just go to www.iTunes.com? My computer is Dell and runs Microsoft, not iOSX.

Can I use Mac FaceTime without having an iPhone?

I recently got a Mac. With every friend, ill call them, talk for a few seconds and then it'll hang up. Is it because I don't have an iPhone? Cause this mac is the only apple product I have.

Websites to download free music on iphone?

I used to have a blackberry and would always use tubidy to download music. I liked it because the sound was pretty good and it was quick. The music also went straight to my library, with my legally bought music. Is there a website like this for iphone 6 where it goes straight to itunes? I tried tubidy but it doesn't download, it just plays.