[multiboot usb help]

nope wrong sorry

ok you have boot.bt3 where your referencing your bootbt3 folder take the "." out of both refernces and try again

[multiboot usb help]

I know what the problem is as stated earlier you have the menu.lst as a text doc so your gonna have to uncheck the option "Hide extensions for known file types"

this will show that you have menu.lst.txt

Just delete the .txt and save

Should work now!