I bought a MP3 Player mainboard from one of those known sites and did some research about it. It was produced by Corporate Systems Center (CSC), a well known american company btw. The model is called MP3 CD Blast-It!, a pro audio product.
Well after a while i had the idea to put it in a case but didn't know which one would suite. After few looks again to some sites on the internet i found an old Betamax Videoplayer for sale - bought for a few bucks! Now then it was time to complete the missing parts to finish this project. A 40x4 LCD display was the greatest problem to catch as well for cheap - but nevermind i did organize it as well from a site :) and it was a green illuminated one which i appreciated. An ATX Powersupply and other parts were taken from my hobbybox.
Next step in future when i got time for it, will be propably adding a phone jack in front and put some small control speakers into the case. Also a bigger Harddisc is in mind since meanwhile the one inside is full :)