OK this is the problem
I needed kernel2.6 for some driver. I updated to it. and I can't go on the internet anymore. I found out I needed ne2k_pci module and I installed it. But it still won't work.

When I do "modprobe ne2k_pci" I get the following:
WARNING: Error inserting 8390
(/lib/modules/2.6.7/kernel/drivers/net/8390.ko): Invalid module format
FATAL: Error inserting ne2k_pci (/lib/modules/2.6.7/kernel/drivers/net/ne2k-pci.ko): Invalid module format

actually I don't know if I can do modprobe :-s.
What could be the problem?

Thanx

What version of modutils are you running?
/sbin/modprobe -V

Perhaps you only have a version compatible with 2.4 kernels. Newer versions are backwards compatible.

I updated modprobe from version 0.9.14 to 3.0 but it still doesn't work

I think the module itself might be wrong. Where did you get it from?

I downloaded the kernel sources from www.kernel.org. And installed them. I thought the module was included.

OK, I found it.
When I was configuring the kernel I (stupid as I was) selected for processor family 368 in stead of 468.