Ala ću sada da se izlajem ako si bot al' ajde.
The problem is probably with resolution. Your avi files are probably 600x400 resolution and your player supports 100x80 or so. As Chivan said, try some software from disc wich came with the player. I also had one chinese mp4 player but it worked flawlessly until I broke it.
Oh, and I almost forgot, are you sure that the player uses avi. Mine used some obscure format but text on the box says different.