It was a mistake, I forgot to load extmod module (all the time I was pretty sure,
that there was 'Load ...' line in my config file
Sorry for talking nonsense about nvidia drivers. They work just great, at least MPlayer looks satisfied with XVideo mode. Thanks for your help.
Oh, just to answer your questions.
I'm using PLD (Polished Linux Distribution, a distribution developed mainly on my University in Warsaw), but the XFree86 comes directly from the XFree86.org, and I must say it works preety stable for me (I use it on my laptop (with Intel I830M video card, which isn't supported by earlier versions of Xwindows) too. By pretty stable I mean that it hangs sometimes, when I'm using new Intel I830M driver, and framebuffer at the same time and I'm trying to switch to text console. So unless you're using strange hardware you can work on it safely. Besides, this version has many useful improvements over 4.2.1, but that's not the subject of this newsgroup.
Once more, thanks for your help.