When upgrading from Windows Server 2008 R2 Standard (OEM) to Enterprise (MSDN) using DISM, some administrators encounter a peculiar issue where only 4GB of installed RAM becomes usable despite proper BIOS detection. The system shows "Installed memory (RAM): 72.0 GB (4.00 GB usable)" while marking the remainder as hardware-reserved.

• Remote Desktop configuration disappears after upgrade
• Occurs specifically when transitioning from OEM Standard to MSDN Enterprise keys
• Using generic KMS client key temporarily resolves the issue
• System becomes fully functional (RDP + full RAM) with KMS key but remains unlicensed

The core issue stems from Windows' licensing validation subsystem. When upgrading from OEM to volume license media, certain components fail to properly initialize memory management and remote services. This creates artificial limitations resembling 32-bit OS constraints.

The correct procedure involves fully removing OEM licensing components before applying the MSDN key:

# First uninstall existing license
slmgr /upk

# Clear existing activation data
slmgr /cpky

# Install new MSDN Enterprise key
slmgr /ipk XXXXX-XXXXX-XXXXX-XXXXX-XXXXX

# Reset licensing status
slmgr /rearm

For production systems, consider performing a clean install:

1. Backup using Windows Server Backup
2. Boot from MSDN Enterprise media
3. Select Custom installation
4. Install to existing system partition (files preserved in Windows.old)

After applying either solution, verify RAM availability with:

wmic MEMORYCHIP get BankLabel, Capacity, Speed
systeminfo | find "Total Physical Memory"

After upgrading from Windows Server 2008 R2 Standard (OEM) to Enterprise using DISM, many users report a strange limitation where only 4GB of installed RAM becomes usable, despite the OS showing the full physical memory installed. The Resource Monitor typically shows the remaining memory as "Hardware Reserved".

This issue primarily occurs when:

• Upgrading from OEM Standard edition to Enterprise using DISM
• Applying certain product keys after the upgrade
• The system fails to properly validate the new licensing tier

The temporary solution that works is to use the generic KMS client key for Enterprise edition:

slmgr /ipk 489J6-VHDMP-X63PK-3K798-CPX3Y
slmgr /ato

However, this isn't a permanent solution as it uses an unlicensed key.

For those using MSDN keys, follow this sequence:

1. First, install the generic KMS key as shown above
2. Reboot the server to verify full RAM is available
3. Then apply your legitimate MSDN key:

slmgr /ipk YOUR-MSDN-KEY-HERE
slmgr /ato

If the above doesn't work, consider a clean install:

# From Windows PE or installation media
diskpart
select disk 0
clean
convert gpt
exit

# Then proceed with normal Enterprise installation

While this is primarily a Windows licensing issue, ensure your BIOS settings are optimal:

• Memory Mode: "Optimizer" (not "Advanced ECC")
• NUMA: Enabled
• Memory Remapping: Enabled if available

After applying fixes, verify with these PowerShell commands:

# Check total and available memory
Get-CimInstance Win32_PhysicalMemory | Measure-Object -Property Capacity -Sum | % {[math]::round($_.sum/1GB,2)}

# Check licensing status
cscript c:\windows\system32\slmgr.vbs /dli

If RDP settings disappeared after upgrade, reset them via registry:

Windows Registry Editor Version 5.00

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server]
"fDenyTSConnections"=dword:00000000

[HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp]
"UserAuthentication"=dword:00000001

Then restart the Terminal Services service.