Hi
Is the Windows disk a genuine version or copied ?
Have you made sure that all the power cables are connected, that is the 24 pin and the 8 pin ?
What power supply have you got driving it and how old is it ?
Are the memory modules in the right slots ? Try using just one stick in the first slot and if that doesn't help swap it with another one.
Make sure that you have Optimised BIOS Defaults loaded ion the BIOS.