If XBox is connected to the REAR input sockets on the VCR.
Press 0, 0, 1 on the Emerson remote, to select VCR's rear socket (L1).
If XBox is connected to the FRONT input sockets on the VCR.
Press 0, 0, 2 on the Emerson remote, to select VCR's front socket (L2).
Also, see here...
http://www.xbox.com/en-US/support/hardware/xboxconnect.htm
(If there is a setting on the XBox for the video output type, eg. RGB/S-Video/Composite, it may also need to be set to Composite Video (CVBS)).
Cobweb, October 2005