I used to place a license at the root directory of each of my computers which stated something to the effect of, "By permitting your software to be installed on this computer ...". No illusions of effectiveness, but I also had questions of the effectiveness of license agreements that were inside shrink-wrapped boxes that were non-returnable if opened, along with conflicting license agreements for the same piece of software (each of which said they overrode the other).

I gave up on that practice after moving over to open source software since (a) most developers select one of a limited number of licenses and (b) I am usually forgiving of mistakes as long as the other party isn't benefiting from those mistakes (e.g. being paid for a product that does not deliver on their promises).