I would have similar problems with an android phone, when the battery had been allowed to die completely. Despite plugging it in to charge, there was no charge indicator and no sign of life. Plugging it in to the PC (with Kies installed) via USB didn't give any indication of the phone being attached.
I found that leaving it on mains charge for a couple of hours, then removing the battery, waiting a few minutes, and then reinserting the battery allowed me to restart the phone.
Both are right on the battery charging and or warranty path.
The Kies software allows the phone to be plugged into a PC USB port and have it show up like a usb disk. However, you can also use android apps to have the phone share files over SMB, FTP, bluetooth, so there are other options as well.