Dell Dimension 4700 won’t post.

This is the problem…Where you turn it on and the fan speeds up real fast’ faster than normal, but the PC doesn’t POST. Additional info…No beeps,No video,No rear
indicater trouble lights,Board lite green,and front power lite L/S green,R/S flashing Amber. Followed Dell trouble shooting sequence to point of everything removed except RAM,CPU,Video Card,and HD.
I swapped out these also. Any help???