How to reset Administrator password Windows Server 2003 installed on Vmware?

I typically use a Linux rescue CD for this purpose. My preference is the PLD Rescue CD, which is a standard part of my toolbox. PLD includes the chntpw - NT SAM password recovery utility, which allows blanking or modification of the Windows password file. Assuming some Linux knowledge, this process works reliably. More details at: http://linuxbasement.com/content/changing-nt-passwords-with-linux-and-chntpw

• Download the ISO image to your vCenter host or client system.
• Boot the VM off of the image (Modify BIOS to boot from CD first, if necessary).
• Once the Linux rescue boots, the Windows drives are unmounted. fdisk -l will show the drive partitions. Let's say that the C drive is listed as /dev/sda2 (although, this may be different on your system). You can mount the drive (C:) to the Linux mountpoint, /mnt using the command: mount.ntfs-3g /dev/sda2 /mnt
• Navigate to the directory containing the SAM file, cd /mnt/windows/system32/config or /mnt/winnt/system32/config.
• Run chntpw -h to list options. The default is chntpw SAM, which will provide menu options to change the Administrator user's password. I usually blank it and reassign upon reboot. You can also assign a new password at this point.
• Change out of the Windows filesystem directory using cd and unmount the partition, umount /mnt. reboot and the system should come up.

All the Live CDs you've tried don't support virtual hard drive created by VMware. To get the Live CD to recognize the virtual hard drive, you need to add the VMware SCSI Disk Controller driver into the Live CD. You can download the driver from this link.

If you don't know how to inject the VMware SCSI driver into the Live CD, you can follow this guide to reset your lost admin password. The guide has included a boot CD which supports VMware SCSI hard drive already.