Why the 64-bit version is available:
http://isoredirect.centos.org/centos...2.1.x86_64.rpm
Add a new CemtOS5.repo file to your /etc/yum.repos.d/ directory which has the following;
[centos5]
name=CentOS-5
mirrorlist=http://mirrorlist.centos.org/?release=5&arch=$basearch&repo=os
gpgcheck=0
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos4
[centos5updates]
name=CentOS-5-Updates
mirrorlist=http://mirrorlist.centos.org/?release=5&arch=$basearch&repo=updates
gpgcheck=0
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos4
[centos5plus]
name=CentOS-5-Plus
mirrorlist=http://mirrorlist.centos.org/?release=5&arch=$basearch&repo=centosplus
gpgcheck=0
enabled=0
gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-centos4
Then try: yum install mysl-server --enablerepo=centos5