Why my pc not start when i put a 2gb 800MHZ ram in slot

Solution
from the ASUS site on that motherboards specs
2 x DIMM, Max. 2 GB, DDR2 533/400 Non-ECC,Un-buffered Memory
Dual Channel memory architecture

I don't think the motherboard is able to use DDR2-800

https://www.asus.com/Motherboards/P5GCMX/specifications/

R_1

Expert
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from the ASUS site on that motherboards specs
2 x DIMM, Max. 2 GB, DDR2 533/400 Non-ECC,Un-buffered Memory
Dual Channel memory architecture

I don't think the motherboard is able to use DDR2-800

https://www.asus.com/Motherboards/P5GCMX/specifications/
 
Solution