to see whether this helps, try to remove the old VMware Tools from one of the VM's manually (Add/Remove Programs), then reboot the VM and try to install the new VMware Tools.
Okay, I don't have time to wait for you to tell me which version of VMware Player 5.x so this covers the current VMware Player 5.x releases...
As a workaround to whatever is causing the issue, download the Guest Appropriate Tarball and untar it. Then execute the resultant executable and this will silently install the VMware Tools ISO Image File to the Working Directory of the VMware Product. There will be no overt indication, hence "this will silently install..." however you should then be able to install VMware Tools the Virtual Machine normally. If it will not install normally then you can attach the Guest OS Specific VMware Tools ISO Image to the CD/DVD and start the install in the Guest from there.
For VMware Player 5.0.2 Build 1031769 - VMware Tools Installer Packages for Windows Host Systems
