I found the instructions on this site worked very well for increasing my VM boot disk size:
http://d3planet.com/rtfb/2009/09/21/increase-vmware-workstation-virtual-disk-size/
Most important thing for me: the diskpart command worked for me with a Windows Server 2008 VM. It did NOT work for me to attach the drive to another VM, as when I tried to boot my original VM again the virtual disk was hosed. As I recall, this is a problem I’ve had in the past.