Okay, this is a stupid n00b question, but it is sufficiently stupid and n00b that Google has yielded no help with it.

I need to edit autoconf.h.

When I try to go to /lib/modules/2.6.13/build/...
I can get as far as /lib/modules/2.6.13/, but build is not a directory - but some mystery file ending with @ - build@.

I was thinking that I had installed the kernel and modules properly, given that kernelversion is 2.6, which matches the findings of both modprobe -l and dir /lib/modules/. What have I screwed up?

It's a symbolic link. If you type ls -l /lib/modules/2.6.13/build it'll show where it's linked to. Probably /usr/src/linux. The @ symbol signifies symbolic link. In other words the real file is elsewhere.

the directory you're looking for is a symlink to your kernel source directory, if it has red color and @ at the end, it means that the symlink is broken (you don't have the kernel source directory). So what you should do is install the kernel source (I see you're using the test kernel from Slack 10.2), just insert your Slackware CD 2, go into the testing directory and install the kernel-source packages. Do a 'ls -al /lib/modules/2.6.13/' and you'll see where the symlink is pointing, in your case it should be pointing to /usr/src/linux-2.6.13 . Try it, and post back with the result.

Right... simcox1 beat me to it .

got it - thanks!