Update help.

Hi.I'm trying to update my iphone 5 as I think I should but I keep getting the message saying 'iphone cannot be found'. I've updated and restarted comp with security installed and turned off windows firewall as it can cause conflicts? I'm also having trouble downloading pics from the phone as it keeps saying' catastrophic error, unable to download'

This is my second iphone and have only had probs since upgrading last year.

Any help appreciated.