Desktops: IBM Desktop Problem

IBM Desktop Problem

We are using IBM desktops at our company, some of the desktops were lying idle (around 20 of them) as we were not using them for the time being were packed and sent to our storage room. These machines were checked before being packed and were running allright. Since we needed the machines again after a period of about 5 months, these when unpacked are not working except 3 of them, which are different models.
When I press the power switch the processor fan runs for a second and shuts down, another desktop when i plug in power cable the machine starts up and power switch does not work.
I have checked the SMPS power output with a multimeter, power is ok. Also I have changed the RAM,battery and the SMPS from a working a machine. There was a considerable quantiity of dust, I disassembled the whole machine and dusted. Nothing is working. I am planning to disassemble again to clean the PCB with some spirit. I would not have placed this on a forum if it would have been 1 or 2 of them, hard to believe all motherboards are gone.
Most of them are IBM 8175 or IBM 8288.