Thanks a lot for your reply and all this useful information Fra, it really helps me!
A lot of interesting things you posted. I'm really gonna get a closer look at those preludes from Bach. I listened to some midi's, wich are on that link you posted, and some pieces really sound interesting, though, it are only midi's, so I'm gonna check if I can get some real recordings of it.
I'm gonna check out some of those Sonatinas too. You posted some composers who I didn't know yet, so I'm gonna listen to some of those, since I always like to hear pieces from composers which I never heard before.
And thanks for all those links with books. I really have to buy some of those, to replace a teacher a bit I guess.

I really have to work on my musical theory knowledge, cause that isn't my best "skill".
Well, time for me to work now. I really like the BWV 936 Prelude in D-moll, by Bach, so I think I might take a closer look at that piece. Maybe it's still too difficult at this stage, but I give it a try anyway.
EDIT: a little bit off topic, but to get back again a bit about the Chopin Prelude Op 28 No 4: I uploaded some versions of this piece and they're all different.
Ver. 1: https://rapidshare.de/files/9217589/CCE_v06CD1_-_04-Prelude_Op.28-No.04_in_Em-Largo.mp3.htmlVer. 2: https://rapidshare.de/files/9217663/05._Chopin_-_Preludes_Op28_No.04.mp3.htmlVer. 3: https://rapidshare.de/files/9217719/14_Chopin_-_Prelude_In_E_Minor.mp3.htmlVer. 4: https://rapidshare.de/files/9217805/07_Prelude__4_In_E_Minor__Op._28.mp3.htmlVer. 5 (a video, the one Sergio Tiempo plays): https://rapidshare.de/files/8287037/Chopin_prelude_No_4.zip.htmlI listened a lot to all of them and for me, it shows me that the pianist is kinda "free" to decide how he wants to play a piece like this and how he wants to let the people feel when he plays it. Like I said, I like the one Sergio plays the most, not cause it's a video, but I just like the way he plays the Prelude Op 28 No 4.
I know I didn't opened this topic about Chopin's Prelude Op 28 No 4, but it can't harm.

Anyway, for the ones who look at this and download some of the versions; enjoy!