When Windows 2008 R2 is installed in an XCP 1.1 VM, the xs-tools install into C:\Program Files (x86)\Citrix\XenTools, not C:\Program Files\Citrix\XenTools as specified by Constants.XenToolsPath.
To work under both x86 and amd64 versions of Windows the XenToolsPath constant should be replaced with a variable that is initialized using the value found in Install_Dir of the HKEY_LOCAL_MACHINE\SOFTWARE\Citrix\XenTools key in the registry.
Log of failure follows:
2012-04-25 15:08:02,987 [4] INFO AgentService [(null)] - Agent Service Starting ...
2012-04-25 15:08:03,034 [4] INFO AgentService [(null)] - Agent Version: 1.0.28.0
2012-04-25 15:08:09,508 [4] INFO AgentService [(null)] - Exception was : The system cannot find the file specified
StackTrace Was: at System.Diagnostics.Process.StartWithCreateProcess(ProcessStartInfo startInfo)
at Rackspace.Cloud.Server.Agent.ExecutableProcess.Run(String fileName, String arguments) in c:\Jenkins\workspace\ci.test.guest-agents.win.apple\src\third_party\openstack\guest-agents\windows\xenserver\src\Rackspace.Cloud.Server.Agent\ExecutableProcess.cs:line 54
at Rackspace.Cloud.Server.Agent.XenStore.Read(String key) in c:\Jenkins\workspace\ci.test.guest-agents.win.apple\src\third_party\openstack\guest-agents\windows\xenserver\src\Rackspace.Cloud.Server.Agent\XenStore.cs:line 30
at Rackspace.Cloud.Server.Agent.XenStore.GetCommands() in c:\Jenkins\workspace\ci.test.guest-agents.win.apple\src\third_party\openstack\guest-agents\windows\xenserver\src\Rackspace.Cloud.Server.Agent\XenStore.cs:line 34
at Rackspace.Cloud.Server.Agent.CommandQueue.Work() in c:\Jenkins\workspace\ci.test.guest-agents.win.apple\src\third_party\openstack\guest-agents\windows\xenserver\src\Rackspace.Cloud.Server.Agent\CommandQueue.cs:line 39
at Rackspace.Cloud.Server.Agent.ServiceWork.Do() in c:\Jenkins\workspace\ci.test.guest-agents.win.apple\src\third_party\openstack\guest-agents\windows\xenserver\src\Rackspace.Cloud.Server.Agent\ServiceWork.cs:line 32
at Rackspace.Cloud.Server.Agent.Service.ServerClass.TimerElapsed(Object sender, ElapsedEventArgs e) in c:\Jenkins\workspace\ci.test.guest-agents.win.apple\src\third_party\openstack\guest-agents\windows\xenserver\src\Rackspace.Cloud.Server.Agent.Service\ServerClass.cs:line 56
