Today I found a nice tool published by Sun© that can be used for converting almost everything into a vmware readable format.
You simply can convert Microsoft Virtual PC or Microsoft Virtual Server.

According to my opinion the best thing about it is that you can create vmware readable file (e.g. for vmware server, player) out of a backup of a physical computer (as far as I know only Windows is supported).

On one hand the Vmware Converter is available as a starter version and on the other hand as a business solution. Former can be downloaded for free here.