screen "no signal"??

[magnusson]

my PC died on my when i turn it on it says "no signal" and then "power saving" and turns it off, i tried switch screens but that dint work, so i was thinking is my graphics card dead or the computer?? yes its an old computer 4-5 years, its a dell dimension 5150, i changes the graphics card a while back and more memory(GeForce GTS 250, 2gb ram) if that helps...