To me it seems strange to use something subliminal when actually you just want to get a message through to your brain - why make it more difficult to understand the message?
I think the main benefit of CDs is to remind you what you are trying to change - keep you focused on the goal - nothing magical or mysterious.
I've just spent a whole day editing video of testimonials about how good Aloe Vera products are - And guess what - Now I want to go and get some Aloe Vera to see how good it is.
So I guess you could record a CD with your message to self over and over - probably just as effective as anything else - if you believe it is
Anyone want to buy some Aloe Vera? - I got a good price

- I got a video about it - you wanna watch it - 10 times
