WARNING, IT IS A TECHNOLOGICAL PROCEDURE ONLY FOR TECHNICAL REQUIREMENTS.
IS STRICTLY FORBIDDEN TO REMOVE PASSWORD FROM VIRTUAL MACHINES NOT UNDER ITS ADMINISTRATION.
DO NOT SEND ANY MAIL ON THE SUBJECT, BECAUSE I DO NOT WANT TO HELP THOSE WHO COULD USE THE INFORMATION FOR PURPOSES NOT LAWFUL.
WE ACCEPT NO RESPONSIBILITY FOR ANY OF THE ABOVE.

If You have a VmWare Virtual-machine and you have lost Administrative password, you can resolve using a simply procedure.

Create a copy of the Virtual Machine and work with the copy.
It work for XP and other Win machine (depending of version of the CD image).
Download ISO image of CD from http://pogostick.net/~pnh/ntpasswd/
Is a GPL program of Petter N Hagen.
Save it in a directory.

Open VMWare Player and Edit the Win virtual machine.
If not exists create a CD device.
Under 'connection' of the CD device, select link to the CD-iso image.
After start of virtual machine the ISO is started, for other actions see documentation for Petter N Hagen routine.
Normally you have to accept all defaults, at end select the user (f.e. Administrator) where to remove password.
At end confirm with Y.
Remove the link to the iso image of cd.
At restart the virtual machine don't require password.

Vmware is a beautiful product, it exist a free tool named VMware Converter that can transform a phisical machine to a virtual machine.
So you can create a opened copy safely.