Sometimes when in a hurry you check the “don’t show me this again” to get rid of a box and then later on realise that it would be quite useful to have this box pop-up.
AutoCAD and LT has a way of restoring these that does not require deep diving into registry or settings files.
Just go to Options, System and click on the Hidden Message Settings button.
Once clicked you will get another dialog box where you can check the ones to restore from hidden and then click OK.
More information can be found at the AutoDesk help file here.