Just to have mentioned that as well ..
Vmware server can run under Linux, and it can run under Windows as well. (As an excample Windows XP or Windows 2003 server.)
To get started learning to use it, it will be much simpler and easier to install it on Windows XP than on Linux/Centos.
Vmware (and sme server) on Windows XP will work, but will possibly not perform as well as when running at Linux/Centos.
So the most easy way to get started learning to use Vmware, and learning to use SME server will be to have Windows XP installed on the single PC, and then install Vmware on the Windows XP installation and then a virtual installation of SME server 7.3 on Vmware.
I have been using such an arrangement on one of my laptops for a while, so I know it will be working. The only drawback is that the Vmware will slow down the Windows XP system a bit. When I use Vmware server on Windows XP I have 2 Gig of ram on the Laptop. I guess it can run with Vmware/SME server also with 1 GiG ram, but not less than that. (In general, virtualization will require more ram.)
To install Vmware on Linux is slightly more difficult, but I have a few notes on that subject if it should be required.
Windows XP with Vmware and SME server is also an option to get started, if there is only one PC. (RAM should be 2 GIG.)
In this way it is also possible to install different Linux servers on the same Windows machine, like SME, Centos, Ubuntu etc.
Later on, when there is two PC's, it is possible to run one host system with Linux and one with Windows, and to move/copy the virtual installations between the two host systems for modifications, testing out, etc. (So if there is something stange with my virtual SME server running on Centos 64/Vmware, I can just copy it over to Windows XP/Vmware to do some more safe testing.)