It keeps telling me to check signal cable on the monitor screen and I cannot even see a post come up but I do hear the hard drive working. This make no since and I have trouble shooted everything and every part in this PC. All parts are getting power and the monitor has been tested on 4 other PC's. Every part in this PC is brand new I even replaced the Monitor cable it's self along with all the cables in the PC and I don’t even get any error beeps.

New parts

9800 GT 512 DDR Video card
ASUS Motherboard factory repaired 4 days old
CPU new
4 gigs Ram new
Mother board
500 Watt PSU
CPU fan
2 HD's with system installed SATA
DVD new
Windows XP Pro new install

If you are not getting a beep I would suspect the motherboard.

Try removing the RAM and boot. If it doesn't beep like crazy you have either a bad motherboard or case speaker.

ASUS Motherboard factory repaired 4 days old

Can you elaborate on this?

If this was RMA'd can you give a bit more history? Perhaps it was not properly repaired.

The first board was sent back to ASUS and they resent me a brand new board like brand new never repaired or used not the old one again

monitor has been tested on 4 other PC's

But have you tried a different monitor on that PC? Did you connect the extra power lead(s) directly to the graphics card?