I had this issue working on a clients server recently.
Issue : Whenever the server ( Windows server 2008 Sp1 ) was rebooted , the memory diagnostic started running.
If you try to Use Esc key to kill it, the server would restart the diagnostic.
Resolution :
This Issue indicates that there may be problem with the hardware. After research and discussion with the client came to this resolution:
Removed the Memory diagnostic from the boot sequence using WinRE
bcdedit /bootsequence {memdiag} /remove .
This offers temporary relief as we can get the server to functional state.
Client will run hardware diagnostic on the server provided by hardware manufacturer.