64 Bit OS
From KlavoWiki
NOTE: This does not seem to be necessary with CentOS 6.0
Once Linux is installed and if you are running a 64 Bit OS, removed any i386 packages and update yum so no i386 packages are later installed.
yum –y remove *.i386
and edit /etc/yum.conf
exclude=*.i386 *.i586