I read on a web page that you could set a password with SET PASSWORD. I tested it (it worked) but now how do i delete the passowrd? I tried SET PASSWORD"" but now it still asks me for a password (but there is none, i just have to press the ENTER key). I still get to BASIC, but i don't want a password on my MSX. How do i delete it?

The clockchip of the MSX 2 keeps in memory only one of the three following instructions :
SET PASSWORD, SET PROMPT and SET TITLE.
With SET PROMPT, you can replace the "Ok" that comes after each BASIC command. (Example : SET PROMPT "Ready"
With SET TITLE, you can add a short text on the screen with the MSX logo, when you start the MSX (Example : SET TITLE "Yes". If the text has more than 6 characters, you must press on a touch to pass this screen. You can also change the colors of this starting screen, by adding ",1", ",2", ",3" or ",4" after the text.
If you use SET PROMPT or SET TITLE, the password is lost !

IIRC there's a key or a key combination to press during booting of your MSX which results in passing the password routine.
Can't remember what/which though.
(it could be the 'stop' key?!)

(that is if you don't know the password... to reset password folow mars's suggestion)

GRAPH + STOP = skip password indeed