Because a disk IS corrupted.
Bad disk
If your Windows operating system gets corrupted, you can start the computer using the boot disk and repair the damage.
It looks like your hard disk has corrupted file or the hard disk has crashed.
It Must Be That The Disk Or Media Is Corrupted.
If the computer thinks your C: drive is invalid, you need to reload the operating system. In those conditions the disk has become corrupted or the OS has been trashed by a virus. If you have a disk in either the floppy drive or the CD drive and the computer is trying to bootload from there, just remove the disk and it should boot ok.
IF you meant 'what is a corrupt hard disk' - it's the internal mass-storage in a computer. If it's 'corrupted' it means the information cannot be read.
by putting it in the disk slot thingy, then go to my computer and it should say there is a disk there, double click it...
A file can be corrupted on a floppy disk any number of ways. Some of the more common ones are whenever you put the floppy disk near a magnet or some other source of ionized metal, if you try and pull the floppy disk out of the tray before the computer is done reading or writing it, or even if you somehow expose the inner part of the floppy disk to any type of electronic device (because of the electromagnetic waves that the electronic device gives off). As to how to retrieve the corrupted file, I don't know of any way to retrieve it.
It may not be a virus. It could be a faulty hard disk or fault ram or a corrupted operating system
There may be issues in either the disk, the programme has corrupted or the computer/games machine cannot accept the format
Insert the install disk for your version of Windows. When your computer starts, it will read the data off the disk, and boot that way. You can then re-install the corrupted files for the operating system when it starts. You should also update your anti-virus software and do a complete scan, as a virus can often corrupt these files
Replace the corrupted command.com with the command.com from your OS system disk.