Okay, I activated my copy of Windows Server 2008 R2 (Evaluation Copy) after a clean install using a DreamSpark
key via the Systems Properties
"Change Product Key" link:Before
So it seems that DreamSpark keys work, like AsciiWolf said in this
I think that it is better if you use the Evaluation DVD instead of the DS IMG as you can have 240 days free if you just need a copy for testing in a VM instead of creating new e-mails and then just getting rid of your VM when you are done testing, but it is always good to have one (main) copy activated with a product key. So you should activate your "main" copy of Server 2008 R2 using a DreamSpark key and then just use the actual Evaluation part if you need to test software in VMs.