Please My N900 doesnt starts and turn off, only appears the nokia logo and close and turn off, I pick the power button and start and the ligth of the front appears like if begin the system but it cant works, urn off, why can I DO? PLease I spend so much money,

You do not mention if you have tried leaving it to charge for a few hours BEFORE trying to turn it on.

Relax. It has happened to others, you can fix it.
First, try starting it with the charger plugged in. Then:
See this page. Note that while the page is called 'updating the firmware', you're actually reinstalling it.
Follow the instructions. If you have problems or the reflash doesn't help, post again with details

Well the battery was in good level of charge, I dont know if is the battery, or other cause, and I have two weeks, with the phone, without any trouble, I navigate in some many webpages, using the phone to another cellphone, but today after to navigate in ovi store, I saw that the desktop turns in some kind of rectangles and turn off the system and I try to restart and restart and pick the power button, but the only screen that appears is the nokia logo and after turn off. PLEEEAASSSEEE HEEEELLLPPP MEEEE.

THANKS FRIENDS... I m going to do In my house, because I havent the charger right now, because I just happen a few minutes ago in this moment, In my work and sawing porn.. jijijij in the bathroom... jijij Im from MEXICO and I hope that my english isnt be confuse for you...

Have you tried removing battery for few minutes? maybe some hardware went to strange state and soft reboots are not able to properly initialize the device? I have seen some bug related to SGX, for example.

I saw your comments, and I need install in windows the software in case to need restart the system. OK thanks friends. Is a good option, One more question.. for you...

You are already excited for the NOKIA N900 or no anymore?

because Im happy with the phone, and with this disappointed, but If you tell me about there is a solution, maybe I have to considerate to stay gratefully with the phone.

OK I going to remove the battery and see what happens ...

Isn't works removing the battery, I will tell you what happens, I pick the power button, and the LED turn in on and after appears the logo NOKIA only (without the hands) and disappears and the little LED in front turn in on and turn off , and the system DONT initiate... perhaps is necessary to utilize the charger as a second option, and after try to reinstall the system from a PC with windows. do you believe that is not a trouble.?

When turning phone on, do you see five points (four dark, one bright) where white point moves? During normal n900 start white LED shines, Nokia logo appears, then five points are visible, initial animation is displayed (with hands and music), then again five points, and then normal desktop appears.

With firmware pre-PR1.1 there was a problem in which when phone was not properly started for 17 times it hanged during start-up on screen with those five points. This was fixed in PR1.1 (2.2009-51), so if you have not upgraded your phone this might be your problem. If you have upgraded it,
I have no idea what is reason of your troubles.

Nonetheless try fully charging the phone and if it does not start then try reflashing. If it does not help - take it to the service.