Drive C is formatted as a primary partition, FAT32, and already set active. After booting the computer with the MS-DOS 7.10 boot disk downloaded here, I ran "SYS C:", then set it to boot from the hard disk and restarted, but it still can't boot from drive C into DOS (I checked and the three files "IO.SYS,MSDOS.SYS,COMMAND.COM" are already in the root directory of C). Why is this? (The hard disk definitely has no bad sectors or anything like that; it's completely intact.)

