If you want to install Android on your N900, there is a guide here...

Normally, nothing should go wrong, but for me some things went wrong... So I decided to write a guide here!

*THIS WILL FORMAT YOUR MICROSD, SO BE SURE TO GET A BACKUP FIRST.*
*IT'S IMPORTANT TO READ THE WHOLE ARTICLE FIRST, AND THEN START... BE CAREFUL NOT TO SCREW THINGS UP.*

*I'M NOT RESPONSIBLE FOR ANY PROBLEMS WHICH MIGHT OCCUR. IT'S NOT LIKELY ANYTHING WILL HAPPEN, BUT I CAN'T BE HELD RESPONSIBLE.*
*YOU MIGHT HAVE TO ADD THE EXTRAS-DEVEL REPOSITORY, TO YOUR SOURCES IN ORDER TO BE ABLE TO GET ALL THE NEEDED PACKAGES.*
*IF YOU HAD ANY PROBLEMS, YOU MAY COMMENT HERE, AND I'D BE HAPPY TO HELP.*

Let's start by installing "rootsh", from here using your application manager...

Now open a terminal and type these:

sudo gainroot

(You will become root user)

apt-get install nitdroid-installer

(This will install the NITDroid installer package)

Well, everything should work now yes? But it doesn't!

nitdroid

It will format your MicroSD and it will create a vfat partition on it... Then it will try to create the next partition, which is ext3... But it will not!

Now that you have all the dependencies, it's not hard to install the right version! There is no official fix yet... Here is what you need:

http://downloads.nitdroid.com/nitinstaller/nitdroid-installer_0.2.7_armel.deb

You can download this from your PC and then get it on your N900, or just download it from your N900 using the browser... You can also use "wget".

Anyway, when you had the file, go where it is... You can use the 'cd' command to go to that directory, or just give the full path to the file:

dpkg -i nitdroid-installer_0.2.7_armel.deb

Now:

nitdroid

You just need to type "YES" and wait... When it's done, reboot your N900 and see the boot loader... You'd know what to do from now on yourself!

But... If you have the enhanced kernel for power users (mostly used for overclocking among N900 guys), it will not boot!

So, what do we do?

apt-get install kernel-power-bootimg

apt-get install --reinstall multiboot-kernel-power

This should add kernel-power to your boot menu.

If you ran into any installation problems, while installing the nitdroid-installer package at first, just run:

apt-get -f install

If it didn't work, and you couldn't install the nitdroid-installer package, you need to download the dependencies. But be sure to download from the Maemo repository. If you install from Debian's, you may have problems.

I suggest you ask on NITDroid and Maemo forums, and also here if you ran into any problem you thought might be important.

Also, I'll write this here, so that you'd not do what I did out of curiosity...

DO NOT ADD DEBIAN'S MIRRORS TO YOUR SOURCES.LIST FILE... OR IF YOU DID, READ THE NEXT ARTICLE I'M GOING TO WRITE. IT'S ABOUT THE PROBLEMS WHICH WILL OCCUR, AND A SOLUTION.

Enjoy NITDroid (Nokia Internet Tablet Droid) now!

(Although I think Maemo is better than Android, Android might be good for playing Android games, showing others your N900 can run more than one OS, etc!)