None of the pre-built vmmon modules for VMware Server is suitable for your 
running kernel.  Do you want this program to try to build the vmmon module for 
your system (you need to have a C compiler installed on your system)? [no] yes

Using compiler "/usr/bin/gcc". Use environment variable CC to override.

What is the location of the directory of C header files that match your running
kernel? [/lib/modules/2.6.20-15-generic/build/include] 

Extracting the sources of the vmmon module.

Building the vmmon module.

Using 2.6.x kernel build system.
make: Entering directory `/tmp/vmware-config1/vmmon-only'
make -C /lib/modules/2.6.20-15-generic/build/include/.. SUBDIRS=$PWD SRCROOT=$PWD/. modules
make[1]: Entering directory `/usr/src/linux-headers-2.6.20-15-generic'
  CC [M]  /tmp/vmware-config1/vmmon-only/linux/driver.o
In file included from /tmp/vmware-config1/vmmon-only/linux/driver.c:80:
/tmp/vmware-config1/vmmon-only/./include/compat_kernel.h:21: fel: expected declaration specifiers or "..." before "compat_exit"
/tmp/vmware-config1/vmmon-only/./include/compat_kernel.h:21: fel: expected declaration specifiers or "..." before "exit_code"
/tmp/vmware-config1/vmmon-only/./include/compat_kernel.h:21: varning: typen sätts skönsmässigt till "int" i deklarationen av "_syscall1"
make[2]: *** [/tmp/vmware-config1/vmmon-only/linux/driver.o] Fel 1
make[1]: *** [_module_/tmp/vmware-config1/vmmon-only] Fel 2
make[1]: Leaving directory `/usr/src/linux-headers-2.6.20-15-generic'
make: *** [vmmon.ko] Fel 2
make: Leaving directory `/tmp/vmware-config1/vmmon-only'
Unable to build the vmmon module.

For more information on how to troubleshoot module-related problems, please 
visit our Web site at "http://www.vmware.com/download/modules/modules.html" and
"http://www.vmware.com/support/reference/linux/prebuilt_modules_linux.html".

Execution aborted.