PC connectivity

[Sonyme]

I have a Fujisu Siemens desk top wth VGA output and a HDMI socket. The monitor is a Wharfedale TV with standard pc 'D' input. It is also HD ready and has HDMI input socket .At present the set up Is VGA- DVI adapter and standard cable which is satisfactory. I have now got an HDMI cable and when this is connected to Pc and monitor and HDMI is selected on TV input source I get an on screen message "No Signal". and nowt happens.!.When using HDMI connectivity does the PC have to receive an instruction and if so - What and how!. Any ideas??