what should i do if moniter reads no signal when you turn on your computer

what sould i do when your moniter reads no signal when you turn your computer on

I get the No Signal message after the normal Windows XP display which lasts for about 10 seconds after switching on. Monitor works fine with another PC. PC sounds OK.
have removed RAM and wiped contacts, blown out dust.
Anyone with other ideas?

here are possibilities:
1. video cable is not connected to monitor to CPU box.
2. video cable is defective.
3. video card is defective.
4. video card driver issue.
you'll not go far from these ideas.