Your description does indicate that the harddisk may have failed.

I would:

1. Try to boot with a Windows Startup Disk and then try to switch to
C:. If the Startup Disk cannot see C:, then I would try to reset CMOS
to its default settings and repeat the experiment. If the default CMOS
settings do not allow access to C:, C: is probably dead. (I hope you
have made backups of everything on C: that you cannot afford to lose.)

Operating systems have distinct procedures for accessing CMOS.
Sometimes they display a command when the computer first starts up,
such as "Press F1". Otherwise, you need to consult the documents that
came with your computer or tech support at the company that made it.

You can obtain a Windows Startup Disk at:

http://www.bootdisk.com/

Bill Starbuck (MVP)

Most hard drive manufacturers have diagnostic software
available for download.

Maxtor   http://www.maxtor.com/en/support/downloads/index.htm
Seagate   http://www.seagate.com/support/index.html
Western Digital   http://support.wdc.com/download/index.asp

Ben