I have a server running Windows Server 2008 Enterprise. I need to purchase a license key for it. Can I purchase a license key for Windows Server 2008 Enterprise R2? Will that work without having to reinstall the OS? Right now its asking me to activate Windows. I really don't want to reinstall the OS because i've been running a trial version up to this point and have quite a bit on the server. Thoughts? And where is the best place to buy the OS key? Thank you!!