My dad has a HP desktop a804n. It worked perfect, he shut it off then the next day went to turn it on and nothing happens.

The monitor screen stays blank (the monitor lights up blue when it's on but now it's just amber/orange). I see no lights on the keyboard and i assume the mouse doesn't work either.

The fans turn on, the cd trays open/close but nothing else. And the power light on the tower just stays a solid amber/orange.

What could be the problem???