Last year, my Monitor (An HP f2105), got a "No Input Signal" everytime I turned it on. The screen would turn purple before going to sleep.
Took it to the store, they said I can use it without a Graphics Card. I did. My games sucked. So, this summer I bought the EXACT SAME Graphics Card that came with the Computer (A GeForce 7500LE), and I still get the same message (No Input Signal). The monitor works fine, I'm using it now, without the Graphics Card. I removed all drivers and re-installed them.