(I have also posted this on technet but I'm running out of ideas)

I've upgraded from Windows Server 2008 R2 Standard to Enterprise in order to make use of more RAM. The server previously had 32GB of RAM.

The upgrade from Standard to Enterprise, using DISM, seemed to go OK, so I powered down and installed the RAM. This a Dell Poweredge T710, I was taking it from 32GB to 72GB.

The BIOS recognised the RAM, although I needed to change from "Advanced ECC" to "Optimizer" mode for it to use all of it.

After rebooting, windows can see the RAM but in the system panel will display:

Installed memory (RAM): 72.0 GB (4.00 GB usable)

In the resource monitor, the remainder of the RAM is showing as reserved for hardware. I've tried various RAM configurations, including reverting it to the same chips and same configuration as before the upgrade, but always just 4.00 GB is showing up as usable. Following some threads on these forums I've gone into msconfig and set the maximum memory "by hand" but that doesn't fix the problem. BIOS doesn't seem to have anything that looks like memory remapping which is another suggestion that has come up.

How do I make this RAM available to Windows? It was available before the upgrade, because I could use the full 32GB RAM the server had to start with.

A screenshot (this is after reverting to the original RAM configuration)

http://screencast.com/t/5FuzevdNb

I don't know if it's related, but my remote desktop configuration has also disappeared: screencast.com/t/mYedomeQWS

(the bottom half of this dialog should allow me to configure Remote Desktop, it was working before the upgrade but now it isn't).