Is there an upgrade for 2003 Standard R2?

[Guest Marcio]

I have a couple of Windows 2003 Standard SP2 servers (Dell PE OEM)

which I want to upgrade to R2 for the DFS-R feature, but I'm having a

hard time finding a Windows 2003 Standard R2 upgrade to buy. It's not

listed here either:

http://www.microsoft.com/windowsserver2003/howtobuy/licensing/pricing.mspx

 

Is there not an upgrade option, and I just have to buy full versions?

 

Thanks.