Why can't I merge these two movie selections when using PowerVCR II?

To ensure the smoothness and quality of movie playback, pay attention to the following items when merging video files:

(a) Merging video files recorded with different MPEG profiles is not allowed. For example, merging a MPEG-1 file with MPEG-2 files.

(b) Merging files with different video profiles is not recommended; for example, merging files recorded by two different profiles that possess different designations such as "Constant Bitrate" versus "Constant Quality".

(c) Merging movie files of different resolution is not recommended. For example, merging files with a resolution of 320x240 and 640x480.