Trying to connect Acer aspire M3641 to Sharp aquos TV via hdmi.

Your TV might have to be on the correct input already for it to show up on available displays on your computer. Set it back to default res and refresh, then look up and see exactly what input the hdmi uses, go to that input, then try to connect to it on your computer.

I have tried that already but it was a no go,  

The Acer Aspire M3641 has an integrated NVIDIA GeForce 7100 GPU on the motherboard. Is the onboard GPU disabled and you are using the NVIDIA GeForce 9800 GT add-in graphics card? It's not clear in your quote which GPU is enabled and which GPU is disabled.

On which port and on which GPU is the Sharp Aquos TV connected to?

How would i find out if the GPU is disabled? And when i bought the pc i also bought the 9800gt and had it put in As for GPU its just a Hdmi lead from my computer to my tv. I only have 1 hdmi port on my PC and 2 on my TV, On my tv it is plugged into HDMI 1.

What is the make and model of the NVIDIA GeForce 9800 GT graphics card? The minimum power supply requirements for a 9800 GT graphics card is 400 Watts (with +12 Volt rail current rating of at least 26 Amps). I thought that the Acer Aspire M3641 came with a 250W power supply. Was the power supply upgraded?

Usually by plugging in a video card into the PCI Express x16 slot the onboard integrated GPU (in your case the NVIDIA GeForce 7150 Integrated Graphics) is automatically disabled. Since you only have 1 HDMI port in your computer I have to assume that it is connected to the NVIDIA GeForce 7150 Integrated Graphics, which is most likely disabled.

Is your computer monitor plugged into a port on the NVIDIA GeForce 9800 GT graphics card? If it is, that would confirm that the NVIDIA GeForce 7150 Integrated Graphics is disabled and therefore the HDMI port is disabled.

I have solved it now the hdmi port was using the integrated graphics so i went to swindon today and got a DVI-HDMI converter alls working now apart from sound

Too bad you couldn't swap your NVIDIA GeForce 9800 GT graphics card without an HDMI port for one that has an HDMI port.