I've been trying out VMware server for a while using different guest OS. On all of them I've seen the same thing - a lot of CPU is used when accessing the host's disks from the guest. The System process is using the most. I've tried with both Windows 2003 and 2008 as host OS with the same result. I'm using the standard bridged network setup.
I would be grateful for anything I could try to get the CPU load down as this problem makes the setup quite unuseful.