Windows 7: Help! No signal when i connect my pc to my tv

I recently bought a LG 55" Tv it has a pc setting so i use my vga cable to hookup my tv to my pc. But it says no signal when i switch to pc mode. I have a Gateway® FX6803-25.

Check device manager for driver.

Please go to start>search>type device manager.
Are there any "unknown devices" with yellow triangles on them?
Is you driver there , listed, and working?

If your driver is missing, or there is a yellow triangle on it, you will need to update it.

nope

If you were using an computer monitor previously that was using a higher non - Vga resolution, Ex - 1920 x 1080 then you may have to go into display properties and switch to a lower Vga supported resolution, Ex - 1024 x 768. It is also a good idea to check in the Bios ( if applicable ) if video output is set to on board or PCI-E.

Also if your TV and computer support it a DVI or HDMI connection will yield much better picture quality and higher resolutions.

well ok then i have a hdmi cable that i could use but when i hook it up to my pc to my tv it still says no signal.

My pc monitor has a native resoulution of 1920 X 1080 and my tv is the same.