And allso, i decided to install X, but i wonna startup in console mode, how do I do that ?
This depends on the distribution you're using, but there's a file, /etc/inittab, that you'll need to edit (in superuser mode.) so that your box won't automatically put you in X.
Find 'id:[number]:initdefault:' near the top of the file (the number can be any number between 0 and 6; I don't know what your /etc/inittab looks like) and, depending on which distribution you're using, you replace that number with some other number between 0 and 6 that will put you in text mode on startup.
Copy and replace 'id:[number]:initdefault:' with the stuff below depending on your distribution. Remove all quotes.
o For most distros: 'id:3:initdefault:'
o For Debian, things get a little tricky... reply for more information.
Edit: I didn't notice that you run Ubuntu, sorry.
This is what you'll need to do (forget everything I said about /etc/inittab):
o open up a terminal (as root)
o type 'cd /etc/rcS.d' without quotes
o type 'ls' and find the one(s) that have anything to do with x11 (ex: S70x11-common).
o assuming the only one you have is S70x11-common, then type 'mv S70x11-common K70x11-common' if you have more, then do the same with the rest.
check the top of inittab to see which number is between the "id" and "initdefault." type 'cd /etc/rc[number].d' and type 'ls' to find the one that has gdm in it (mine is S21gdm, yours might be different) , and type 'mv S21gdm K21gdm' replace '21' with the number between S and gdm.
o Voila! Reboot, and see if it worked.