I recall that back in the mists of time there was software that promised to help with this, but I don't think it worked (like the software memory enhancer). Really, there isn't much you can do about screen burn - that's what the screensavers were for. I suppose the whole screen could be burnt some to lessen the noticablility of the burnt bit but that seems counter-productive. As pointed out above, it's teh phospors in the film on the CRT that get the burn, and there's no way to service the inside of the tube without destroying the tube.