Install Plesk on Cent OS 5.2

Important Pre-Installation Tasks:

Login to the VPS Hosting/server & execute "uname -i" to get the OS bit version so that you can download the appropriate installer package.
[root@server ~]# uname -i
x86_64

Run the following 3 commands, to check if Apache, PHP & MySQL are preinstalled by the OS:
[root@server ~]# rpm -qa | grep -i http
[root@server ~]# rpm -qa | grep -i php
[root@server ~]# rpm -qa | grep -i mysql

If the above are found to be installed [most of the time they are] by the OS, they conflict with the applications Plesk installs, hence remove them using..
[root@server ~]# yum remove http*
[root@server ~]# yum remove php*
[root@server ~]# yum remove mysql*

Check SELinux status, we have it disabled but still... execute "getenforce" it should say "Disabled" or "Not enforcing". If it's enforcing, disable it by executing: "setenforce 0".
root@server [~]# getenforce
Disabled

Once done, download the Auto-installer utility that suits your operating system from HERE and save it on your server's hard drive.
eg : [root@server plesk]# wget plesk_auto_installer_file_name

Set the execution permission for Auto-installer:
eg : [root@server plesk]# chmod +x plesk_auto_installer_file_name

Run the Auto-installer:
eg : [root@server plesk]# ./plesk_auto_installer_file_name


Ref:
http://www.eukhost.com/forums/f15/how-install-plesk-control-panel-linux-vps-dedicated-servers-5434/
http://www.parallels.com/en/download/plesk8/