Centos – Mysql 5.5 is not installed in CentOS 5.7

I am using CentOS 5.7 with 64 bit. In my machine already have MySQL 5.0.88 version. Now I want to upgrade MySQL to 5.5 version. I followed this link to start my installation process. When i give "yum --enablerepo=remi,remi-test list mysql mysql-server" it's ouput like

     -> yum --enablerepo=remi,remi-test list mysql mysql-server
 Loaded plugins: dellsysid, fastestmirror
 Loading mirror speeds from cached hostfile 
 * base: ftp.iitm.ac.in 
 * epel: buaya.klas.or.id  
 * extras: ftp.iitm.ac.in 
 * remi: remirpm.mirror.gymkl.ch
 * remi-test: remirpm.mirror.gymkl.ch 
 * rpmforge: mirror.oscc.org.my 
 * updates: ftp.iitm.ac.in remi             | 2.5 kB     00:00   
   remi-test                                | 2.5 kB     00:00    
  Available Packages mysql.i386                 
    5.0.95-5.el5_9                                                 updates       
    mysql.x86_64                                                  
    5.5.30-1.el5.remi                                       remi   
    mysql- server.x86_64                                           
    5.5.30-1.el5.remi                                       remi

When I run "yum --enablerepo=remi,remi-test install mysql mysql-server" command it returns

-> yum --enablerepo=remi,remi-test install mysql mysql-server
Loaded plugins: dellsysid, fastestmirror
Loading mirror speeds from cached hostfile
 * base: ftp.iitm.ac.in
 * epel: ftp.jaist.ac.jp
 * extras: ftp.iitm.ac.in
 * remi: mirror5.layerjet.com
 * remi-test: mirror5.layerjet.com
 * rpmforge: kartolo.sby.datautama.net.id
 * updates: ftp.iitm.ac.in
Setting up Install Process
Package mysql is obsoleted by MySQL-server-community, trying to install MySQL-server-community-5.0.88-0.rhel5.x86_64 instead
Package MySQL-server-community-5.0.88-0.rhel5.x86_64 already installed and latest version
Package mysql is obsoleted by MySQL-server-community, trying to install MySQL-server-community-5.0.88-0.rhel5.x86_64 instead
Package MySQL-server-community-5.0.88-0.rhel5.x86_64 already installed and latest version
Package mysql-server is obsoleted by MySQL-server-community, trying to install MySQL-server-community-5.0.88-0.rhel5.x86_64 instead
Package MySQL-server-community-5.0.88-0.rhel5.x86_64 already installed and latest version
Nothing to do

It seems link 5.0 is the latest. Please help me how to upgrade MySQL 5.0 to 5.5