VM Guest OS Upgrade just attach vHDD (VMDK)

Hello,

I have a VM running Windows Server 2003, it is simply a file server with a vHDD(VMDK file) of 1TB.

The OS is installed on a seperate vHDD (VMDK file).

My idea is create a new VM running Windows Server 2008 with the same windows domain name, and simply attached the old 1TB VMDK file to it, and present the new disk to the new Windows 2008 Server.

Is it as simple as that? do I have to watch out for anything, as I dont want to break the original 1TB VMDK file.

Thanks