If you are running a CentOS 5.4 on a Virtual Private Server (VPS) with no Control Panel at RackWire.com, yum does not come installed by default.  To Install yum on CentOS 5.4 run the following commands:

rpm -ivh –force http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/yum-3.2.22-20.el5.centos.noarch.rpm http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/python-elementtree-1.2.6-5.x86_64.rpm http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/python-iniparse-0.2.3-4.el5.noarch.rpm http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/python-sqlite-1.1.7-1.2.1.x86_64.rpm http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/rpm-python-4.4.2.3-18.el5.x86_64.rpm http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/python-urlgrabber-3.1.0-5.el5.noarch.rpm http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/yum-fastestmirror-1.1.16-13.el5.centos.noarch.rpm http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/yum-metadata-parser-1.1.2-3.el5.centos.x86_64.rpm http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/m2crypto-0.16-6.el5.6.x86_64.rpm http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/libxml2-2.6.26-2.1.2.8.x86_64.rpm http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/nss-devel-3.12.3.99.3-1.el5.centos.2.x86_64.rpm http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/nspr-devel-4.7.4-1.el5_3.1.x86_64.rpm http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/pkgconfig-0.21-2.el5.x86_64.rpm http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/pkinit-nss-0.7.6-1.el5.x86_64.rpm http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/nspr-4.7.4-1.el5_3.1.x86_64.rpm http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/libselinux-devel-1.33.4-5.5.el5.i386.rpm http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/libsepol-devel-1.15.2-2.el5.x86_64.rpm http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/elfutils-libelf-devel-0.137-3.el5.x86_64.rpm http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/elfutils-libelf-devel-static-0.137-3.el5.x86_64.rpm http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/rpm-devel-4.4.2.3-18.el5.x86_64.rpm http://mirrors.rit.edu/centos/5.4/os/x86_64/CentOS/sqlite-devel-3.3.6-5.x86_64.rpm

Enjoy and Contact RackWire.com Support if you need any assistance!