I've got this server running on a local Hyper-V host, but can't log in because I don't know the username and password for it.
http://vmdepot.msopentech.com/Vhd/Show?vhdId=147&version=254
I set the server up as a Virtual Machine in Azure, then stopped it, and downloaded the VHD from blob storage.
When you set up a vhd from VM Depot, you had to go through a few steps, including downloading the baseline image to your own storage account and then registering the image as one or your own usable images. At that point, you're able to spin up brand new Virtual Machines based on that registered image. During that Create Virtual Machine step, you're prompted for all sorts of stuff, like VM name, cloud service name, and ssh username and password/certificate. After that final set of questions, a new VM is spun up, with an associated VHD, with your specified credentials set up in the VM.
If you attempted to just download the VM Depot VHD, you won't be able to login to that VHD, as it has no login for you. You must first create a proper Virtual Machine within your subscription. Once that's done, you're free to stop the VM and copy its vhd down to your local machine.
These are the steps I'm referring to, following the registration of the VM Depot image into your own account:
Once the VM is running, take a look at it in the portal. At the bottom, you'll see the actual blob name storing your new OS disk. At this point, just stop your VM and then copy the vhd down to your local machine.