itunes doesn't recognize my iphone 5

Try the procedure in Cerbu's post:

Re: sync problem

... or try section 5 from the following document:

TS1538: iOS: Device not recognized in iTunes for Windows

... but if you still have the same recognition troubles, try a complete uninstall/reinstall of both iTunes and all related software components, as per the instructions from the following troubleshooting document:

Removing and reinstalling iTunes and other software components for Windows Vista, Windows 7, or Windows 8

I had this same problem and Cerbu's procedure worked for me. Just makes me wonder what went wrong in the first place.