hi, I just brought an N800 Tablet and for some reason its not powering on. Can anybody help me to turn this on.

You tried turning it on with the charger plugged in?

Yes, I tried that, but nothing.

Is it "new" old stock that you bought? If so, it likely has the old bootloader (which has issue powering on). In which case, you'll have to wait it out. These instructions should help.

You must keep the power button pressed until the screen turns on.

And make sure it's been charged first. Plug it in and let it charge for a good amount of time. At least half an hour, preferably 2.5 hours.

i'll try it and see,thanks.

So... it should be charged up by now, have ya had any luck?
As previously mentioned, the button needs to be depressed a good 3 - 4 seconds for the critter to power on.
Slight hijack but related; what's the average number of times a battery can be recharged before it starts to croak, anybody know?

A few hundred times I think. My battery will be 2 years old in January, it started to show a slight degradation in capacity (as in quicker to drop a bar) 2 or 3 months ago. Nothing to worry about yet though. The change is small enough that I'm only 70% certain that I'm not imagining it.