I have just bought this computer from grabalaptop.com but I did not get a user guide as it was refurbished and I have tried to get one on line but when I put the computer number in it cannot find the model it has a model number on my receipt and another on the laptop the one on my receipt is HP Compaq nc6120 but the one on the laptop is HP Compaqnc6320 and I am not sure which numbers on the underside is the model number can you help david