Worked perfect before. So far, I have replaced the psu and video card.
Motherboard is ASUS P5Q3 DELUXE
CPU IS 2.83 Quadcore
all the fans go on, HD shows activity
But there is nothing but a black screen.
Time for preventive maintenance. Pull all cards and modules and clean them and reseat them. Blow out case and and optical drives with canned air. Disconnect and reseat all cable ends.
Since it has been sitting for 8 years, pull the CPU and redo the heatsink paste.
Also check your monitor. You should pull the outside case and blow it out with canned air. They can collect dust through their vent holes. And check the cable connections while you're at it. Check that it will work with another computer.