I have a Slackware 9.0 whit kernel version 2.4.20
I tryed to compile the 2.4.21 version but this error occours:

make[3]: Entering directory `/usr/src/linux-2.4.21/net/core'
...
...
gcc -D__KERNEL__ -I/usr/src/linux-2.4.21/include -Wall -Wstrict-prototypes -Wno-trigraphs -O2 -fno-strict-aliasing -fno-common -fomit-frame-pointer -pipe -mpreferred-stack-boundary=2 -march=i686 -nostdinc -iwithprefix include -DKBUILD_BASENAME=dev -c -o dev.o dev.c
dev.c:605: redefinition of `dev_get_by_flags'
dev.c:561: `dev_get_by_flags' previously defined here
dev.c:627: redefinition of `__dev_get_by_flags'
dev.c:583: `__dev_get_by_flags' previously defined here
make[3]: *** [dev.o] Error 1
make[3]: Leaving directory `/usr/src/linux-2.4.21/net/core'
make[2]: *** [first_rule] Error 2
make[2]: Leaving directory `/usr/src/linux-2.4.21/net/core'
make[1]: *** [_subdir_core] Error 2
make[1]: Leaving directory `/usr/src/linux-2.4.21/net'
make: *** [_dir_net] Error 2

I don't have any LAN cards, but only a 56k modem.

Who can help me ???

I'd recommend running a
make mrproper
and then start the kernel config all
over, or copy the config of the old
kernel ... be aware that even if you
only have a modem you'll still need
to compile network support into the
kernel if you want to be able to use
the internet (as opposed to to using
your modem for BBS or Faxing solely)

Cheers,
Tink