i did a uname -r which returned 2.4.24-1-386
so then i tried:

apt-get update
apt-get source kernel-image-2.4.24-1-386

which gave me this:
(note that i had to edit out the mirror URL thanks to LQ's "no url's before 5 posts" rule)

Reading Package Lists... Done
Building Dependency Tree... Done
Need to get 95.2kB of source archives.
Get:1 <URL EDITED OUT> testing/main kernel-image-2.4.24-i386 2.4.24-2 (dsc) [1816B]
Get:2 <URL EDITED OUT> testing/main kernel-image-2.4.24-i386 2.4.24-2 (tar) [93.4kB]
Fetched 2B in 0s (5B/s)
sh: line 1: dpkg-source: command not found
Unpack command 'dpkg-source -x kernel-image-2.4.24-i386_2.4.24-2.dsc' failed.
E: Child process failed


Can someone please tell me what the problem is?

Try using "apt-get install kernel-source-2.4.24" instead

thanks, that was it. but here's a stupid follow-up question: now where are my sources located? the nvidia installer wants to know.

usually in /usr/src/

Yep try /usr/src, but the sources won't actually be there -- just the .tar.bz2 file. You'll need to extract it with something like

tar xfjv kernel-source-2.4.24.tar.bz2

And then it should make a directory /usr/src/kernel-source-2.4.24 or something similar. Usually I just proceed to rename it to /usr/src/2.4.24 for easyness