Nine year old computer sounds like it has given up the ghost. Mostly likely a motherboard failure. That means buying a new computer. Only thing worth trying is replacing the $2 cmos coin cell battery. See manual online at Dell Support for how to do it.
The BIST button is not a system Diagnostic Button.
You can get a 390 with windows 10 pro for the same cost as the windows Disk alone.
Bult In Self Test BIST
Solid Amber power button is BAD POWER SUPPLY or DEAD MOTHERBOARD or both.