Unfortunately, you have probably deleted your IO.SYS file. If you had deleted COMMAND.COM, you'd get a "bad or missing command interpreter" messge. Your system would boot without AUTOEXEC.BAT or ...

I have an external eSATA data disk attached to my Macbook Pro, and it crashed this week. Not a major problem, since I do weekly incremental backups with Carbon Copy Cloner & Time Machine is also ...