Running vmware-config-tools.pl script on a guest CentOS 5.1 virtual machine in a VMWare Server 1.0.5 environment will not find the proper kernel modules, so it will prompt you to compile the modules.
To do this you need a compiling environment (namely gcc) and the C kernel headers installed.
If your machine is connected to the Internet, this is easily solved by invoking the following commands:
<prompt># yum install gcc (about 8+ Mb)
<prompt> yum install kernel-devel (about 4.7 Mb)