I posted earlier an article about the newly released R2 Beta release which is available for download on the web for evaluation and preview.
But here is a rule which apparently is not described properly in the download page: if you downloaded the Evaluation copy of the R2 Eval Beta site from the web then you need to know the following:
1) The Product Key for this Eval Beta R2 build will install only on top of the Eval versions of Windows Server 2003 SP1, which is available here.
2) The provided R2 Beta Eval product key will not work when installing Eval Beta R2 on top of Windows Server 2003 SP1 Retail, or Windows Server 2003 SP1 Volume Licensing (VR) Retail.
3) The rules above are not valid if you obtained the R2 Beta build and its associated product key from other methods than downloading from the web from the R2 Eval Beta site. In that case, please consult the associated instructions for your particular build.