There isn`t a floppy left in floppy drive is there?
Or sounds like missing boot files or master boot record.
Remove non system disk. ie: remove the non system disc from floppy or CD-ROM drive.
Alter PC boot sequence in BIOS changing PC`s boot order to start from. Have a device that has boot files (or operating system files) installed on such as Windows disc in your CD_ROM drive.
Rumpel
January 2010