Whenh I power my Dell XPS 600 up I get a solid amber power light and the Dell diagnostic light (1, 2, 3, 4) only shows 4 in green there is no cycling of the numbers at all.
Diagnostic Light Number 4 on its own indicates a MotherBoard related issue.
Generally I have found removing and reseating the RAM to solve this in many Dell PCs. Be careful though if its under warranty i would send it off for repair.
