HDMI giving "no signal" but picture still shows

[Vailixx]

My TV says it has no signal but it is still displaying the conputer background and I can still use it. But it has a giant, "No Signal" box and it isn't in the source list lit up.

 

[Thineswar]

Did you try pulling the cable and putting it back in?
Did you select the tv as the monitor or output on windows and in nvidia control panel?