The first step to being able to boot your tablet off an internal mmc/sd card is to have the rights to make these kind of changes.
What is Root Access?
Root(root) is the name of a unix systems master account. Like your Local administrator or Domain Admin type accounts in windows, root is the end all be all of unix rights.
Why be root?
There are many things that can not be done as a normal user that we will need to do in order to have these extra options.
I am not going to dual boot, should I still know how to be root?
Absolutely. Even if your not going to dual boot, there are many advantages to being root and having root command line abilities.
The n800 is actually a debian linux system. Debian is a distribution of linux, like fedora, or mandriva or my favorite gentoo (google for LinuxMint if you want a reallllly easy ubuntu based desktop linux OS). Debians method of package management is called dpkg (debian package.. clever huh) and a front end for this is called apt. Apt is a tool for fetching and installing .deb files (the dpkg format) and all the files needed to install that file (called dependencies) on your system. Repositories are locations for your system to look online or locally to find these files. Get it? Good. Moving on.
Before OS2008 you had to add a terminal (a command line access to your tablet) from a new repository. With OS2008 nokia has decided to make access to this application a default install with the OS. Big thumbs up to Nokia on that one. However we still need access to the root level account.
Step 1. Install becomeroot
We are going to install a package that lets you become root.. its called becomeroot :-)
The repository that contains becomeroot doesn't work well with OS2008, but you can download the app by itself. From your n800 click on the following link
When the options pop up click "Open", this will run the .deb file in the Application Manager and install it properly.
Step 2. Gain root access
Once your done with that, you need to start the xterm(The console application).
MENU -> Utilities -> X Terminal
From with in xterm type the following
That command will give you your root account. Sudo is a command that lets you run other commands as root, in this case gainroot.
Do be a bit careful as root if don't know linux, as you can cause a lot of problems.
Most of this info was garnered from www.internettablettalk.com and www.maemo.org especially http://maemo.org/maemowiki/HowTo_EASILY_BecomeRoot, however this doc was written to explain whats happening and update for OS2008