How to use OpenProcessToken, AdjustTokenPrivileges, and GetExitCodeProcess in VC++ 2005

Question

I read a couple of posts on how to check if a process has exited from a different process (I realize some people get hung up on semantics here, but just humor me) and I tried to implement it but am running into the error code 5 ("ERROR_ACCESS_DENIED") all over the place.

Here is what I do.

1) Process 1 (P1) launches process 2 and writes to a shared memory location its own PID.

2) Process 2 (P2) reads the PID from shared memory

3) P2 calls OpenProcess(...) with P1's PID to save a handle that it can check later.

4) P2 calls GetExitCodeProcess(...) with P1's PID repeatedly and checks for a STILL_ACTIVE code.

In the above method, I keep getting the ACCESS_DENIED error on GetExitCodeProcess. I've tried modifying P2's privileges by using the below code from MSDN's docs:

HANDLE proc_h = OpenProcess(SYNCHRONIZE, FALSE, GetCurrentProcessId());
HANDLE hToken;
OpenProcessToken(proc_h, TOKEN_ADJUST_PRIVILEGES, &hToken);

LookupPrivilegeValue(NULL, lpszPrivilege, &luid );

tp.PrivilegeCount = 1;
tp.Privileges[0].Luid = luid;
tp.Privileges[0].Attributes = SE_PRIVILEGE_ENABLED;
// Enable the privilege
AdjustTokenPrivileges(hToken, 
                      FALSE, 
                      &tp, 
                      sizeof(TOKEN_PRIVILEGES), 
                      (PTOKEN_PRIVILEGES) NULL, 
                      (PDWORD) NULL);

But I keep getting the ACCESS_DENIED error on the call to OpenProcessToken(...) method. So does this indicate some sort of system level hurdle? I do have admin rights on my machine and I'm running XP.

Thanks in advance for any help.