I have recently bought a used iPhone 3GS. The phone is up and running, except for one minor issue. When I connect the iPhone to my Windows PC, I get the message "Charging is not supported by this accessory" with a yellow triangle and an exclamation mark. It will successfully sync but simply won't charge. I have tried various USB ports and different cables, all official Apple. I have tried restoring the iPhone, reinstalling iTunes etc. It will however charge from my work laptop, so I am investigating the set up of my USB ports on my PC. Any other idea's?