@massits, @RealBlackStuff

Thank you for your suggestions.

But it does not work. I tried both reinstalling ram modules and pushing on the southbridge chip.

Maybe the module to communicate with IDE interface has been completely dead, now I can not find the IDE HDD from BIOS anymore.

My T42 reports an error: ... Video BIOS shadowed UMB upper Limit segment address: DC00 Mouse initialized ... With only the light `power on` turned on, it stalled. But I can enter BIOS utility by press F1, and I can not find my IDE0 hdd from Startup. So I replaced it with a new IDE hard disk, now the...