It's normal to have two vmtoolsd.exe processes.
When you see the high CPU usage, what windows are open in the guest? There is a bug that causes CPU usage if the foreground window in the guest is running elevated, like regedit.
Ok on two vmtoolsd.exe's.
The only window open on the guest is Task Manager.
Does the problem happen with, say Notepad open? Task Manager will be elevated if you have it set to show processes from all users.
It appears not to happen with notepad open, but as soon as taskmanager is open with more details (which I take as the new show all processes name in given in Windows 8's new taskmanager), the cpu usage does goes crazy.
Now, if you have taskmanager open, or any elevated other window as you said, and then do a drag and drop, forgetting all about this detail, what's the way to get everything back to normal, short of rebooting or logging off?
You can use Task Manager to kill the vmtoolsd.exe process that's using 100% CPU. To restart it, you run a command line like this:
"C:\Program Files\VMware\VMware Tools\vmtoolsd.exe" -n vmusr
The exact command line to run can be found in the registry:
HKLM\SOFTWARE\Microsoft\Windows\CurrentVersion\Run, string value VMware User Process