I noticed one of my Windows XP x64 machines suddenly shows a logon prompt for Windows Server 2003 R2. It shows the same prompt during log-off as well. I've always heard that the Windows XP x64 code base was built on Windows Server 2003 but I have never seen this behavior before. And yes, I double checked that someone did not install Windows Server behind my back. A dump of "systeminfo" shows that it is clearly still the Windows XP x64 SP3 installation that I originally put there. I suspect a registry key may be to blame possibly in HKLM/.../winlogon but I really don't know where to start on this on. Especially since I don't know how long the problem has existed so I can't trace it back to a specific moment in time. This computer is in a lab not contected to the internet so I don't suspect foul play (yet). Any ideas?