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.
--
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

Usually a "fully charged" battery inserted freshly after being pulled out for at least one minute from an usb disconneted device solves most problems.

You should install u-boot. From there you can fix and even boot nearly everything. Happy Hacking!

The Nolo bootloader seems ok. So what output do you get with this command?

It could be a driver problem. The device gets recognized but when switching to flashmode it doesn't get recognized again. You can try my flasher/rescue live image.

Boot with the rescue image look if it is working.
Mount your n900 look after kernel and modules for example.

Try to flash it with the live image.

When nothing works the only help will be cold flashing but your flasher still recognizes your hardware so I think it is not needed.

Probably a kernel only reflash would've fixed it.

Taken from this thread http://talk.maemo.org/showthread.php?t=71915

For driver issues check this guide:

As explained on the wiki pages there is no way to just "uninstall" a kernel, you need a kernel to boot.
Your system is in a bootloop which is a normal situation from having a broken root. The device will not charge in this state so it would be advised to charge your battery from another source.

Fully charge the battery from another source, this will also completely power down the device. Also make sure you use the same USB port on your PC as the last time you flashed.

You are right. I made a mistake doing so without reading the wiki pages.
Actually I get another problem now. After I successfully re-flashed my N900. I installed the 'multiboot&multiboot menu.deb'. No modifications have been done after the installation. And when I reboot the phone. It shows this message which leaves no option for me to boot into the original system. I know I made a foolish choice to install something I didn't understand.
Is there a way I could skip this message and boot it normally?
(factory re-flash could be my last weapon)
With Regards

Multiboot is deprecated. You also can't just install it like that it depends on other packages/images.

To tie in with the other thread you posted. You need to fix your repos with the mirrors and get application manager working. Randomly installing .debs to get things working is just going to make a unusable mess.

I have downloaded the 43GB Maemo mrrior. After I extracted it, there were many folders come together. I have no experience of buliding my own local server. My desktop is running windows10 64bit at this moment. That's why I was randomly installing .debs and expecting to get things work.

Any thread in this forum that would teach me build my own local repository step by step ? I tried to use IIS(Internet Information Services) and set the maemo mirror folder to be shared, but it didn't work on my N900. The maemo app manager said it couldn't connect to that server.

Own repo mirror, I would recommend a linux system.
But why? Repos are still online:

https://talk.maemo.org/showpost.php?...5&postcount=50

Wow! Life saver you are !
I didn't notice the Repos are available now.
I used the 'faster app manager' at the first time, it didn't sync with the repos you provided. But it works on the original maemo app manger!
Now I got Wgames, Kmplayer, Open Arena, and all most everything I need on N900.
Big thumb up sir. LOL