For this computer, a solid amber power light means that a device may be malfunctioning or incorrectly installed. Try removing your memory modules and replacing them one at a time. If reaseating the memory does not solve the problem, check other things such as PCI devices, SATA cables, and any other cable that may have come loose inside the computer.

This is what the troubleshooter says in reference to your issue:

• If the power light is steady amber, a device may be malfunctioning or incorrectly installed.
  
  
  • Remove and then reinstall the memory modules (see Replacing or Adding a Memory Module).
  • Remove and then reinstall any cards (see PCI and PCI Express Cards).
• Eliminate interference. Some possible causes of interference are:
  
  
  • Power, keyboard, and mouse extension cables
  • Too many devices on a power strip
  • Multiple power strips connected to the same electrical outlet