When you upgrade from a Windows Server 2003 R2 Standard SP2 to Windows Server 2003 R2 Enterprise Edition SP2 you may have a problem with memory. In case you have more than 4GB RAM on the machine (my situation was with 8GB) you have to do the following:
Locate boot.ini (it should be on the root of C:\ drive)
Under [operating systems] find the entry of Windows (it will be something like multi(0)disk(0)……=”Windows Server 2003, Enterprise” /noexecute=optout / fastdetect
“/PAE” at the end
So now you will have
multi(0)disk(0)…..=”Windows Server 2003, Enterprise” /noexecute=optout /fastdetect /PAE
Restart the machine and now you ‘ll see the correct memory size.