VMware-Server is simply a SERVER application
Windows XP is a game-system and NOT supported
If it runs, fine - If it runs not -> You get warned before install it that your os is not supported
Who enables fast user switching on a work-machine?
I guess XP is out of scope for this VMware application.
BTW, Windows XP is not a "game-system".
This is because we replace MSGINA, in order to hook the shutdown event, in order to implement the automatic shutdown of running virtual machines when you shut down the host. Fast user switching goes away once you replace the stock GINA.
There is no other clean way to implement this on pre-Server 2008/Vista systems. Seriously. See here:
The reason we don't talk about it in the release notes is because XP is not a supported operating system.
If you'd rather have fast user switching and no automatic shutdown support, you can uncheck the checkbox option about automatic virtual machine start/stop that you get when installing Server. (I should add that I haven't actually verified this, but I believe it to be true.)