Missing HDD

[avj]

If you recently added the hard drives you may be looking at a cascading power supply failure these are fairly rare usually if a power supply fails it fails all at once, but sometimes it can fail in stages. Before adding any new hardware to a system I recommend calculating the size of power supply needed to run the new hardware. This is the link to an online power supply calculator that can give you an idea of what size power supply you need.

http://www.extreme.outervision.com/psuca...orlite.jsp

This may not be the problem you are having but it is good to keep in mind.