Hmm…Was the sound when it was acting up kinda like the muted plucking of a guitar string (ie, kinda like a “pop” noise with the tiniest smidgen of reverb?), rather than the normal clickety-clackety? If so, it could very well be that the head arm actuator - the thing that moves the heads back and forth across the drive platters - is about to go. It will probably become more and more frequent until you can boot to it again.
I don’t think it would be your BIOS, or drive cables, or anything like that - 85% of the time in my experience, if the system is booting up, getting past the POST, THEN getting the “Cannot access Drive C:” error while trying to load the operating system AND the drive is making strange noises, then the issue is usually hardware-related.
However, I can think of one other strong possibility - there is a bad segment of your hard drive where the operating system loading data is, and the noise is from the heads trying to read from that location numerous times because it’s not finding data where it thinks there should be data. One way to check is to use a hard-drive diagnostic utility. Scandisk that’s included with DOS/Windows works, and can find different things wrong if doing a surface (aka thorough in the Windows version) scan, but I would actually check the website of the hard drive maker - they have low-level utilities that often find things wrong that Scandisk or other 3rd-party disk utilities just can’t, and can tell you whether the issue is recoverable (ie, re-format the drive, marking those sections as bad), or if the drive is toast.
As I think about it, I am leaning strongly to the second issue. Usually if it’s showing “Cannot access Drive C:”, then that means at least part of the OS kernel has loaded, and is hitting a failing spot when it gets to a certain point in the OS load sequence. If the heads themselves were failing you’d usually get an “Operating System not Found” error. And most of the time I saw other hardware issues (IDE controllers going bad, bad cables, BIOS issues) you would get “Non-System Disk or Disk Error” with no floppy disk in the floppy drive.
A week to fix it? Are they that backed up? If it is a failing drive, it shouldn’t take more than an afternoon to fix it. Easy to do at home, too - I would just go out, get a new drive, a copy of Norton Ghost personal edition, hook up the new drive, ghost the data off your old drive to the new one, and just use the old one as non-critical data storage until it goes “poof”. And I highly suspect that’s what any repair shop would do anyway - at least that’s what I would do if I ran a repair shop.
Hope this all helps!
critter42