[CentOS] Source RPM

Hi All,
      I am using CentOs 4.2  . I need  to change the  kernel rpm . I
downloaded the kernel-2.6.9.EL .src.rpm. after  installing this rpm i
changed  the linux-2.6.9.tar.gz . Bu changing the source i made the rpm. But
gives the error . Is it anyother file also required?? . Can anyone knows how
i can do this ?
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