It was fine early today when I tried to uninstall the 'power-kernel'(Everything is fine when I uninstalled the 'power-kernel'. Maemo5 apps still working, no error shows). After I turned off the N900, it just doesn't boot everymore.

The screen keeps showing Nokia logo(with black screen in a loop)and reboot itself again and again.

At first, I thought the problem was normal that could be solved by rewriting the factory ROM&Emmc(Which always save me when I have a boot issue)

It is different this time !
I used the same factory Rom&Emmc as before. Exactly the same version of 'Flasher-3.5.exe' software.
However, N900 could never connect to my PC again.(32bit windows xp sp3 system/32bit win7 as well)

When I launch the 'flasher-3.5.exe' it can detect my N900 but quickly failed when boot it to 'Flash mode'.
I pressed 'U' keyboard and connect PC with usb cable. The usb icon was showing at the top-right corner of the screen, but Windows xp always says the usb cable is not connected.('N900 flash parent mode' or something)

Has everyone else experienced this situation ?
Is there a way I could save my N900 ?
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Update from 2018/10/1. Thanks for all your help.
My N900 is finally back.
It was something about the 'flash sequence'
As the factory reset files are divided in 'Emmc.bin' and 'Rom.bin', I usually flash Rom.bin after the Emmc.(That's what the Instruction said)
But in this case, I should actually start with the Rom.bin.
I coincidently flashed the Rom.bin file that brought my N900 back. Like the replys pointed out it was a driver issue. The 'flasher-3.5.exe' rejected N900 for preventing possible damage I guess. A several new pictures have been added to the attachment. Maybe someone could figure out a reason.
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At the end, I would like to send my grateful to those who replied at this thread. I am a total newbie who has never been used Linux&Terminal command line before. (couldn't read them as well)
I couldn't get my N900 back without you. Thumb up