I like that. Kinda' rhymes. "Fan OK but no Display"
Problem is your Processor isn't turned on.
You have a bad Power Supply.
> Weak voltage power rail.
You probably have a 200 to 300 Watt power supply. (SMPS)
1) ALL of the LED lights together use less than 1 Watt of power.
2) EACH fan uses 2 to 3 Watts.
3) A typical Processor can use 51 to 125 watts. Depends on what Processor it is.
The Intel D845GVSR motherboard uses a Socket 478 processor socket.
Supports Intel Celeron, Intel Pentium 4, and Intel Celeron D, that utilize a Socket 478 processor socket, and have a maximum FSB of 533MHz.http://en.wikipedia.org/wiki/List_of_Intel_chipsets#Pentium_4_Chipsets
Utilizes the Intel 845GV motherboard chipset.
[ Intel 82845GV Northbridge chip, and Intel ICH4 Southbridge chip ]
89 Watts is the maximum wattage, that can be used by a Processor for the Intel D845GVSR motherboard.
Power Supply has enough power to light LED lights, and spins fans, but not enough to turn the Processor on.
No Processor operating, No computer.
No computer, No video signal to the monitor.
Do you have access to a KNOWN to be good, compatible Power Supply, for a test unit?
Motherboard Manual in PDF file form:http://www.intel.com/p/en_US/support/highlights/dsktpboards/d845gvsr
Under the heading > Documents and Guides, left-click on > Product Guides for D845GVSR.
Then left-click on the first file listed.
Product Guide - PDF File Name: D845GVSR_ProductGuide_English.pdf