Welcome to the CentOS fora. Please see the recommended reading for new users linked in my signature.
Don't use obsolete/unsupported releases - 5.7 is the current release. See the CentOS 5.7 Release Notes
for details. By not updating you are implicitly accepting that you will live with numerous bugs and security issues (and associated known exploits) that have subsequently been fixed.
Who told you not to use NTP and why not? Seems like an unnecessary restriction. On the other hand, if both servers are on VMware then the VMware Tools should keep the time synchronized. If having trouble with time drift try adding "divider=10" to the kernel line in /boot/grub/grub.conf. See the VMware KB Article: Timekeeping best practices for Linux guests