Trying to upgrade my vmware workstation is not always easy on Vista. I was using 6.0.5 and tried to upgrade to the brand new 6.5. I got several O.S. warnings and when I finished the installation Vmware WS didn't work ( problem with DLLs ) . I was unable to uninstall and to roll back to an older version.
Googling I found this technote that solved my problems instantly.