A little background explanation:

Ever since I got my cable modem installed I've had intermittent occasions where the computer just "freezes" for about half a minute to a minute. After that it continues to work normally as if nothing had happened. I found that these freeze-ups tended to go away after I defragmented my hard disk (especially after I've been downloading stuff), and it never happened when the cable modem was off.

Now the real problem:

Well, in the past week things really got bad. If I leave my computer online for several hours, the computer will freeze up for at least ten minutes, and then I get a blue screen saying "Failure to write to C:" (or something to that effect).

Also, every time I start up the computer (online or offline), it says "Improper shutdown detected" while Windows loads up and runs ScanDisk. What's particularly troubling is that ScanDisk is also running a sector scan, which takes a long time (and inevitably results in the "Failure to write to C:" error), so I've been aborting the check. (On the other hand, I've run Norton Disk Doctor on C: several times since this problem's cropped up and haven't turned up any problems at all from NDD.)

This morning I was working my computer offline to take care of some things, and I got the familiar blue screen message, and only about an hour or so after starting up.

I just want to ask if anyone has any idea what's going on. Right now I'm thinking about replacing my hard disk, but I'm wondering if the problem might be elsewhere (motherboard?) and I might be wasting my money (and time) replacing a perfectly good component.

I don't have much time to write a full on reply, but based on what you said, this is what I think:

I would tend to trust Norton WAY more than scandisk. I doubt your motherboard is the problem.

A few months ago my dads hard disk was showing a garbled root directory. I was about to get it replaced, but I figured what the hell, I would swap the signal (ribbon) cable. That fixed it. The connection just needed to be reset. I doubt that is the problem here though.

First, run the manufacturers diagnostics on it. Seagate, WD, and practically all other mainstream manufacturers have utilities you can download off their web site. You run the exe, it makes a boot disk, you reboot, and scan the drive. NEVER low level format it unless you want to lose EVERYTHING. Most all of them can scan the drive without writing anything to the platter. Be sure to run the longest scan possible!

If it reports errors (and these are generally VERY thorough), theres your problem.

A failure to write to drive C is most commonly caused by the following, in no particular order:

1. Drive is full (duh)
2. Controller on the drive is screwed and is misreporting data back to the driver and OS (I had a Seagate drive that every week it stopped detecting the drive, I had to reset the cable each time. I tried 2 different cables. Same thing. Problem: bad controller. Sent it back for RMA, got a new one, problem solved.)
3. The Windows driver is corrupt. You would need to tear it out of the system configuration, reboot, and let Windows reinstall it.

There is a slight chance the ribbon controller could be defective as well, causing the drive to fail to read/write data, but that is pretty rare.

That's all the time I have right now. I first suggestion is to get the manufacturers utilities. I always believe those over scandisk.

And obviously... make sure there is PLENTY of free space on the drive. :)

Can't add much more to Aaron's suggestions. Like him, my first move would be to get ahold of the dignostic utility from the manufacturer and see what it says. Let us know what it reports.

Well, I think the problem's been fixed. When I went to get the HD manual to find the manufacturer's web page, I noticed a little line at the bottom telling me to leave space above and below the hard disk for ventilation and to prevent overheating. The way I had it set up, I had the drive sandwiched between the floppy drive and an older hard drive that had all my original data and that I was using as a backup data drive.

So I transferred all the important files back to my primary drive removed the old drive, and moved the current drive down one slot for ventilation. It's been running for most of the weekend with no major problems. (Still has a tendency to "freeze" for a few seconds while online, but not as bad as it's been recently.) So apparently all my recent problems were due to the hard drive overheating. (Strange that it hadn't occurred before, though.)

Have you thought about adding another fan to your system? I recently added a dual-head air circulation system to my computer. One head draws air in and blows towards my second hard drive, while the other head expels hot air out of the case. May be something you want to look into. I got mine for $20 at Fry's Electronics.