I have a client that has windows server 2008(non r2) 64 bit. They need to be able to work with more memory since they are using hyper-v. So, we need to upgrade to 2008r2 enterprise. If I just buy the 2008r2 enterprise retail or OEM license, how do I accomplish this upgrade the easiest way? Also, they currently have 25 cals for the 2008 server. Will these cals still be legal for the 2008r2 enterprise server? Thanks for all your help.