Starliu, and anyone else who's considering subliminal and sleep learning programs, I highly recommend you check out the book "Your Memory: How It Works & How to Improve It" by Kenneth L. Higbee, Phd. It's one of the best books on memory I've read. It's more academic and scientific than other memory books -- scholarly, well researched, extensive references. Anyway, he's got specific chapters on subliminals and sleep learning and I think you may want to check out his thoughts on the subjects before spending a lot of money of this stuff.
