Device Driver not ready?

[rhodesy]

I have recently bought an internal PnP modem for my Pentium 100 computer. i opened up the computer, slotted in the modem and switched back on.
As the computer began to boot a message appeared saying 'Device note ready - insert boot disk into drive A'
I tried to the start up disk but it won't start Windows, it won't run scandisk and won't allow me to change from a prompt to c prompt.
I looked at the BIOS and couldn't see the hard drive mentioned and am concerned that I have broken the hard drive.
Any ideas please....

[BEOR999]

Remove the case again and check that the HDD cable has not been dislodged, I think you will find that it has been and re-seating the cable will "fix" the fault

[rhodesy]

Thanks for your input. I checked the HDD cables and all seemed fine. Then turned on the computer and things went from bad to worse.
Now there is no visuals on screen and the PC makes three or four beeps and then two further seperate beeps and then nothing.
What next??