Can you tell us your Computer model, and the BIOS name on the first screen you seen during the boot?
I'd also be happy to know which OS of Windows you are using (XP or Vista, etc).
The default boot order is usually:
Floppy/Diskette.
Optical Drive (CD or DVD, etc).
Hard Disk 1.
Hard Disk 2 (if any).
USB device.
Network adapter.
If you wish to change the boot order, on the first screen after boot, it should tell you which button to press to access the boot order options menu / BIOS menu (of which you can find the boot order options menu), if the first screen does not tell you wish key to use to access them, then try F1, F3, F10 or F11.
So do you mean you can't put any CDs/Floppies/USBs in as there are no bootable mediums (trays/entry points) or do you mean there are nothing in the mediums?
I understand the error as I did use to be an IT Consultant and Technician.
It is simply when a virus has corrupted the device driver or the device has been unplugged that the PC boots off, usually the hard drive in this case (probably fallen or blown inside).
If you could access the hard drive at all via the BIOS menu then I can send you an image of the OS disc and its activator.
CybX Systems - ASP.NET MVP.