IPhone 4 Causing Computer to Freeze?

Recently I have been having issues with plugging my iphone 4 into my PC, I'm stilling running windows XP and whenever I try to plug my iphone in via usb, my computer completely freezes and I have to force a shutdowm. What could be the problem?

How to transfer dropbox mp3 songs to iphone 5?

I figured i have to transfer my songs to Itunes first, but I don't know how to sync or anything:/ The songs were from my old phone but it doesn't work anymore so I can't sync it from my old phone. All I have is dropbox. I downloaded the Dropbox app on my Iphone 5 but i can't download my songs from there. Its very inconvenient.

I can't sync my iPhone 4 to my computer. What do I do?

ITunes on my computer which runs on Windows 8 is perfectly up to date, and the Apple ID account on computer and the phone is exactly the same, but whenever I just plug my iPhone in with the USB it doesn't show up as a device that I can sync with. Just nothing shows up and nothing changes.

Just what exactly do I have to do to make it even show up as a device in iTunes?

Will AT&T sell me a SIM card?

I have an iPhone 5 is broken beyond all reason, but an upgrade next month, My cousin gave me a phone, but the SIM card is a different size than mine, will AT&T sell me a SIM card for my cousins phone and let me use it til my upgrade? Or will it count as my upgrade?