[Hampshire] scripts/basic/Makefile missing

Help!

I have ground to a halt trying to build the nvidia driver for the new
2.6.21 kernel. What I usually do first is go into the linux-headers
directory and run

make oldconfig

For some reason this doesn't seem to work any more and I get this:

/usr/src/linux-headers-2.6.21-1-k7# make oldconfig
scripts/Makefile.build:17: /usr/src/linux-headers-2.6.21-1-k7/scripts/basic/Makefile:
No such file or directory
make[1]: *** No rule to make target
`/usr/src/linux-headers-2.6.21-1-k7/scripts/basic/Makefile'. Stop.
make: *** [scripts_basic] Error 2

Have I missed a step somewhere? I tried 'make scripts' and various
other targets like menuconfig, silentoldconfig, prepare etc, but got
similar messages, e.g.:

/usr/src/linux-headers-2.6.21-1-k7# make prepare
scripts/Makefile.build:17: /usr/src/linux-headers-2.6.21-1-k7/scripts/basic/Makefile:
No such file or directory
make[2]: *** No rule to make target
`/usr/src/linux-headers-2.6.21-1-k7/scripts/basic/Makefile'. Stop.
make[1]: *** [scripts_basic] Error 2
make: *** No rule to make target `include/config/auto.conf', needed by
`include/config/kernel.release'. Stop.

I've tried purging and re-installing the linux-headers package and all
its depends but still the same.

TIA, Peter