Missing password
People downloading the publicly available Test Drive images from Microsoft need a user id and password to log on the the virtual machines.
In a recent post Clive refers to Dugie's blog post containing the password information. But there's also a document containing all necessary password and other details describing the content of the downloaded image etc.
After downloading an image you must extract the actual VHD files running the executable piece of the download. After extraction you find a bunch of files besides the VHD/VMC files that make the actual virtual machine. One is a ReadMe.htm. This ReadMe.htm has the user id and password information for the virtual machines.
Have fun playing with the Microsoft provided virtual machines.