'hello.
my nokia 770 is not booting correctly. after the NOKIA logo and sound it shows a white screen for 3-5 seconds and it restarts. it keeps doing this all the time. a month ago I tried to update the software but I couldn't make it.
Any help is really needed and appreciated.

Thank you

Have you changed chargers recently? I've found that my N770 is very particular about the charger that I use. Specifically I have broken the original charger and I've tried two other chargers (one cheap knockoff and one supposed Nokia charger) and neither of them work. I have to use the charger from my N800 to actually be able to charge the N770. Interestingly enough, all the chargers work on my N800, so I know the chargers are not broken.

I experience a similar boot, reboot sequence when the battery is dead on the N770 when it is plugged in but not charging.

I was actually going to start a new thread here to see if anyone else has experienced a similar situation with some chargers not working with the N770.

I bought a second fake battery and a desktop charger which is using the original charger to charge the battery out of the tablet.
I didn't charge the original battery with that charger.
the problem persists with the original battery which is charged the normal way.

Make sure you are using the original charger to plug the N770 in. Let is sit turned off for 15-20 minutes before you try to turn it on.

It may not be related to battery power, but since you've changed things with the new battery and charger, I would want to know conclusively that it wasn't power related before I tried more drastic measures.

I already let it off for 10 days

I think I missed this in your followup post. Sorry. I don't have any other ideas unfortunately.

When does it cycle rebooting? Does it only do it when it is plugged in or does it do it even when unplugged?

If it does it when unplugged, then that would also verify that it is not a battery problem. (When I had the problem with charging, it would cycle when plugged in, but simply die when unplugged).

it's doing it both plugged in and not plugged in.