I doubt very much that the case has an Ir transceiver, think thats the right word, built into it. Loads of motherboards have these Ir connectors on the motherboard, but I have never come across a motherboard that ships with the receiver \ sender. This would be plugged into the M\B and then fitted to the front of the case. As Ir has to physically see each other.
The best way to communicate with a 7650 is to get a usb bluetooth dongle, about £20 with the software. You will also have to go to the Nokia website and download N7650_PCSuite_en. This is the Nokia software that will talk to the phone. It is 26.6meg.
You could alternatively buy a USB-Ir adaptor for about the same, but as I have mentioned above the phone would have to actually see the Ir device.