You should be moving to WinPE for your boot environment rather than DOS as DOS has so many limitations with modern hardware that it can be very time consuming to diagnose issues such as yours where no specific information is provided about driver versions, dos config and autoexec content, protocol.ini and other configuration parameters. Also, if your target PC has a SATA hard disk, you need to make sure that the bios has a compatibility mode to emulate an older PATA hard disk, and the setting is enabled, otherwise the DOS boot will not see the SATA hard disk (since DOS has no SATA support).
SATA based optical drives also have boot issues with DOS as the old CDROM drivers don't work.