The MediaSmart Server is only provided with the minimum Windows Home Server specification of 512MB RAM. Upgrading the memory  is possible on the server, and HP have announced that it will NOT invalidate your warranty.
There is a single 512MB DDR2-533 (667mhz) RAM module inside the server, upgrading to 2GB is a relatively cheap ($50) upgrade, and a good tutorial can be found at myhomeserver.com
The trickiest part of this upgrade can be removing the small screws on the front grill and you will find it easier using a Phillips head #00 screwdriver.
Once the memory has been upgraded, the Pagefile should also be upgraded. This is typically 1.5 times the physical RAM size, but do not place on the D drive, keep it to the system drive.