[CentOS] kernel sourcecode ?

Hi,

I've just installed CentOS 4.2
I must recompile the kernel and for that i used to do a "yum install 
kernel-sourcecode".

Now, it doesn't works anymore.

In /usr/src/kernels/... compiling gives an error straight from the start.

Where is now kernel's source code ?

Warm Regards,
Mário Gamito