Hang on, let me use my psychic powers to find out all the other relevant information including your system specs, monitor and what cable you are using (VGA or DVI etc)
Things I don't understand from your post:
-replacing the CPU would not change the result. Did you perhaps mean other "computer"? I am going to interpret it as such and interpret that through the test you found out the monitor is fine.
In the meantime, try and see if anything here works:
-try the integrated graphics if present
-are there any beep codes on boot?
-pci eh? sounds like an older computer. How old is it?
-try the video card in another PCI slot
-double check that the PCI card is working by trying it in another computer.