Iphone 5 and computer

I have an iPhone 5s and a Windows 8 Toshiba computer, had both of them for about a year and half. And I have problems all the time with the computer, never the iphone. But recently (it's done this before but like once in a great while). I will plug my iPhone in the computer and a thing pops up saying this device is unrecognized, if this occurs again your device might be malfunctioned. And it says it every single time I plug it in now and isk what to do, I've tried it all, and the great thing? No insurance on either one -.- if I get lucky my iPhone ill come up in iTunes but it's rare, it won't sync. It will freeze until I i'm plug it. So any ideas?

Try buying a different sync lead. Sounds like your Sync lead is faulty.

Are there any wires exposed on the sync lead? Is iTunes up-to-date? Are you running iOS 8.1, the latest?