DOS Command Sys
Type: External (1.0 and later)
			
			SYNTAX
			
			SYS [source] d:
			
			Purpose: Transfers the operating system files to another 
			disk. The three files that are transferred are IO.SYS, MSDOS.SYS, 
			and COMMAND.COM (if you are using IBM's version of DOS, they are 
			named IBMIO.SYS, IBMDOS.SYS, and COMMAND.COM). 
			
			Discussion
			
			Using versions of DOS prior to version 4, the disk had to have 
			enough contiguous free space on it for the three files to be 
			transferred. In the newer versions that is no longer necessary.
			
			
			You may not be able to reliably transfer system files to a disk that 
			already has a different version of DOS on it. 
			
			The system files IO.SYS and MSDOS.SYS are hidden files that do not 
			appear when you use the DIR command to display a directory of a 
			system disk. 
			
			In versions of DOS prior to version 5, when you use the SYS command 
			to transfer the system files to a disk, the file COMMAND.COM (which 
			contains the command processor) is not transferred. When using those 
			earlier versions, you must use the COPY command to transfer 
			COMMAND.COM. 
			
			A system disk can also be transferred (along with all the files 
			stored on it) using the DISKCOPY command.
			
			If an error is encountered, SYS will not transfer the system files. 
			DOS will report one of the following error messages: 
			
			Message: No room for system on target disk
			
			Meaning: This message means that there is not enough room on the 
			target disk for the system files. 
			
			Message: Incompatible system size
			
			Meaning: The system files do not take up the same amount of space on 
			the target disk as the new system will need. This can happen if you 
			try to transfer system files to a disk that already has a different 
			version of DOS on it.
			
			You may receive other error messages if DOS cannot find the required 
			system files at the source location specified or if you try to use 
			the SYS command to transfer the system files to compressed drives or 
			networked drives. 
			 
This page is from http://www.easydos.com. I pasted it on my website to avoid possible broken links. For further help with DOS commands, Check easydos.com out.
