Be Careful Switching 
From One DOS to Another
	 
	Although MS DOS and PC DOS are very similar and your computer can run either, if you plan on upgrading your system by installing a hard disk and want to use DOS 3.0 or higher, you should stick with one or the other. The hidden files, IBMBIO.COM and IBMDOS.COM on PC DOS, are different for MS DOS, which can cause "non-system disk or disk error" messages. Once one system is installed on your hard disk, that’s the one you should keep on using.