kernel headers

Hello

I'm afraid i messed my nice knoppix :(
I suppressed the /usr/src/linux-2.4.22 which was pointed by
/usr/src/linux  
and now i can t compile my 2.6.8-rc2 kernel 

the 2.6.8 Doc said: (i read it carefully after !!!)
  Do NOT use the /usr/src/linux area! This area has a (usually
   incomplete) set of kernel headers that are used by the library header
   files.  They should match the library, and not get messed up by
   whatever the kernel-du-jour happens to be.

So now i know i messed up my install :(, how do i get a clean one ?
just copying the /usr/src/linux-2.4.22 from a knoppix CD is enough ?

Thanks 
Alain