The 2.x kernel source is available from http://www.kernel.org Please use an available mirror close to your location to save bandwidth. If you have a recent version of tar, you can download the .bz2 compressed file.
Untar the kernel:
cd /usr/src tar jxvf /path/to/linux-2.4.21-tar.bz2 - for bzip2 kernel - tar zxvf /path/to/linux-2.4.21-tar.gz - for gzip kernel - ln -s /usr/src/linux-2.4.21 /usr/src/linux
Depending on the Linux distribution you have, you may, or may not have the quota softwares installed on your system. The most recent version of quota is available through SourceForge and is in active development. You can reach the homepage of the quota-development at http://www.sourceforge.net/projects/linuxquota.