I simultaneously shot SD and HD video with my Sony NXCAM camera. I edited the SD video in a multicam SD sequence. Now I want to replace the SD video with the HD video in an HD sequence. I tried simply replacing the SD footage with the HD footage, but all I get is the HD footage at 720 x 480 pixels in the HD sequence. Is there any way to replace the SD video in the multi cam sequence with the HD in an HD sequence and see the entire HD frame (rather than seeing only 720 x 480 pixels in the HD sequence). HELP!!

Try this . . .
Make a new sequence with your HD settings (ie: 1080 or whatever HD rez you shot in)

Go back to your SD timeline, copy all the clips and them paste them into your HD timeline.

Then replace the SD footage with HD footage.

See if that works for you.