I'm a bit confused about these pc based diagnostics. Someone on the bay is selling USB pc diagnostic cable which you plug into the socket in the car and USB port of your pc. No interface or anything else needed (apart from software) but what's carsoft, gt1, inpa??? Some need serial port and so I will need serial to USB adaptor which some say works and some say it doesn't. I would be grateful if someone can point me in the right direction .