Hi,I have 4 Dell sx280 units. All of them have the

it would still try to **** if it was a hd problem check the memory slot or the powersupply

Sounds like classic motherboard failure for this model.
Did you buy these secondhand or EBay or in some fire sale...

This model has a well-known history of motherboard failure.
The capacitors used by Dell (purchased from electronics component vendors) on the motherboard, usually surrounding the CPU socket fail.

You can generally tell by looking at then. If the tops are bulged, discolored or leaking, then you have your answer. (There was for a time comments that the ones with an "X" on the tops were prone to fail). The capacitors look like little soda cans, colored metal cylinders, with metallic round tops.

You can solve it by replacing the motherboards, which isn't hard to do, but tedious...and a little pricey. There are also lots of people on google and EBay who will replace all the capacitors for a fee, again tedious but not terribly hard to do.

It would certainly be unusual to expect 4 machines to all fail at once, but maybe some additional info about the history, or source of your units might help.