I was struggling a bit with an incorrect default username my VMware machine was starting with everytime. Everytime I started or reboot the machine, Windows automatically logged on with a default username I don't want to use. This is due to the 'personalize' option during creation of a virtual machine.
Therfore, I first thought it was an VMWare issue, but it turned out it isn't. You need to change something in the Windows registry.
Edit the following key:
Search for the key with the name DefaultUserName and change it to the account you want.