GetPathFromPID

//uses PsAPI

function GetPathFromPID(const PID: cardinal): string;
var
  hProcess: THandle;
  path: array[0..MAX_PATH - 1] of char;
begin
  hProcess := OpenProcess(PROCESS_QUERY_INFORMATION or PROCESS_VM_READ, false, PID);
  if hProcess <> 0 then
    try
      if GetModuleFileNameEx(hProcess, 0, path, MAX_PATH) = 0 then
        RaiseLastOSError;
      result := path;
    finally
      CloseHandle(hProcess)
    end
  else
    RaiseLastOSError;
end;