I tried SuSe 7.3 long time ago and I remember that it should be version of VMware for SuSe. SuSe team placed the libraries to the another location than other distros and nearly every application has to be configured to run on SuSe. In this case it seems that you have kernel 2.6.11.4-21.7 installed and kernel source 2.6.11.4-20a. To be able to install VMWare you need source for the kernel installed, 2.6.11.4-21.7, or kernel for the source.
I do not remember, but if you check in YaST you may be able to find what you need in the software section.