A friend of mine got a DVI to HDMI cable to plug from his graphics card (GTX 280) into his existing Samsung TV that has a HDMI input. When he powered the PC on, it displayed the BIOS fine but when it came time to display the log in screen for windows 7 the TV flicked to a black screen saying 'mode not supported'. Is there a way to rectify this or is there just an irreconcilable difference between DVI from a graphics card to HDMI on a TV? Also, the TV has a 15 pin D Sub input, could this be used with a DVI-D Sub converter on the side of the graphics card?
Do you happen to have two outputs, such as the TV along with another monitor, connected at the same time? If so, remove the second output and leave only the TV. Also, you can try booting up with the computer connected to a working monitor first and plug in the HDTV when you reach the desktop, leaving the first monitor still connected. Then, go to display properties / screen resolution to check if the computer detects two displays. Activate the second display (TV) and set it as your main display.
The computer is just plugged singly into the TV. Unfortunately, he has recently moved quite far away so i was trying to provide some long range support that he could try himself but he doesn't have access to a second monitor to try those things you suggested. Thanks for the tips, i'll keep them in mind for when i manage to get to his computer. For now i've told him to hang fire with a DVI - D Sub cable which is known to work (his laptop does it fine).