Hi. Can you help me?

First this is the story, the owner of an internet cafe consulted me this morning to check two of his PCs (both Celeron).

I press the power to turn it on.

Then it turns on, then after a second or two, it automatically turned off. After again a second, it automatically turns on and nothing appears on the monitor. ((1) turn off, turn on)

I checked it's RAM (PC266 DDR), tried to remove it. Then turn it on, to check if it is the RAM that makes the monitor in black state. Then a sound beeps which means no RAM inserted. But, the thing I wonder is the (1) turn off, turn on did no more on it.

Both PCs have the same problem.

All possible solutions will be appreciated.

It sounds like an overheating issue. The BIOS is shutting down the system.

Check for failing fans.

I suggest a common cause fault if two PCs have the same problem. Say the PCs are left on overnight - there is a power glitch and they get hosed. It might be they were in disk write mode or something like that and only the disk drives are screwed, not the PSU nor motherboard nor RAM.

That sort of thing - common cause fault on two machines.