How do you remove admin user credentials before capturing an image to deploy to the VM depot?

Hello,

I'd like to capture an image of my VM to deploy it to the VM depot:

http://azure.microsoft.com/en-us/documentation/articles/virtual-machines-capture-image-windows-server/

https://vmdepot.msopentech.com/List/Index

However, when I created the VM, I had to create a default administrator username and password, such as "myadminaccount" and "password"

How do I remove those credentials before capturing the image?  I'd like to "generalize" the virtual machine so that it doesn't have my credentials attached to it.

Thanks!

Matt