Unable to copy photos iPhone 4

Hi I cant seem to be able to install my iPhone correctly. I can sync with iTunes fine but cant copy photos and videos across.
In my device manager it says iPhone under imaging devices but with an exclamation mark. I have tried to update driver but once it starts to install digital imaging device it says cant install data is invalid.
This may have been discussed elsewhere but I cant find the thread.
If anyone can help or at least point me in the right direction please.
Ally
Dell Windows XP