Do I need to get worried if my external HD keeps getting undetected?

[Paul Keith]

Not sure if this is a hardware or a software problem but I've had two XPs experience this already when the external Hard Disk would be detected and then undetected and then redetected again.

[mouser]

this happens to me sometimes -- im not sure why but sometimes i think because i need to power it up BEFORE connecting the usb.
i wouldn't worry about it.

the real worry would be if your drive is detected but windows has errors reading the contents.

[Paul Keith]

I don't think that's the problem mouser. I've had 3 power switch requiring external HD and one mini-one that doesn't have it and it happens.

The problem with ignoring this is that it happens quite a lot. Ex. I just have this happen 5 times now just right now so I can't access the disk.

[Darwin]

What kind of enclosure are you using (Firewire or USB or other)? What kind of interface is/are the drive(s)? I have found that perfectly fine SATA drives in USB enclosures pretty much WILL NOT WORK with XP. I suspect that I've had a couple of cheap and nasty enclosures - can you swap the affected drive into an enclosure that you don't have this problem with? OK, I'm rambling now 

[Shades]

I assume you have an external harddisk enclosure with separate power supply? When the harddisk enclosure houses a 3,5 inch harddisk that is very likely the case.

First, check if the power supply plug is correctly seated. Then check the USB cable between the harddisk enclosure and the PC it is attached to.

Sometimes a plug on either end is not seated correctly. If that is not the problem, try a different cable. When the external harddisk works without problems with the different USB cable, it is very likely that one or more of the lines in the old cable is broken and should be replaced.

If that is also not the case, open the harddisk enclosure and check if the cables between the harddisk and the internal controller are seated correctly. When they are seated correctly as well, the possible points of error are its power supply, harddisk or controller.

To be sure, remove the harddisk from the enclosure and connect it to a free SATA or IDE port on your PC. Test the harddisk by copying from this disk to your regular harddisk (saving your important data!) and writing to this disk, read out its S.M.A.R.T. information etc. If this goes ok, then your harddisk is not the problem.

At this point you can still try to exchange your power supply with one from the same type that you know works well and test the harddisk again in its enclosure.

If this also not works then it is very likely that the controller is broken and you should consider buying a replacement enclosure.

[Paul Keith]

Sorry guys, these questions are kind of too advanced for me.

I don't really know whether these are SATA drives. That has always confused me.

Shades, I don't think that is the cause because even though my past external HDs had this problem, this one is a Western Digital MyPassport without a power supply plug and is using a different usb cable.

[4wd]

... but I've had two XPs experience this...

-Paul Keith (November 23, 2008, 02:15 PM)

What exactly does this mean?

Two installs of XP on the same machine OR two different machines both running XP?

Whenever I've had this type of problem, (disconnect/reconnect), with an external USB anything it has always been the physical USB connection itself that was the cause.

eg.
1) Broken wire in the cable.
2) Contacts on the plug are recessed into it too much and don't make correct contact to ones in the socket.
3) Contacts on the plug are too short(!) and don't reach the contacts in the socket.
4) Contacts in the socket have been bent by someone pulling out the plug at an angle.
5) Contacts in the socket are too short.
6) Connection from front mounted USB ports to motherboard has come loose.
7) USB port on PC too tight and plug not fully inserted.

Honestly, USB ports give almost as much trouble as the old serial ports.

Shades, I don't think that is the cause because even though my past external HDs had this problem, this one is a Western Digital MyPassport without a power supply plug and is using a different usb cable.

-Paul Keith (November 23, 2008, 08:40 PM)

If you mean it's powered by the USB port itself, (ie. it's a 2.5" drive), then are you plugging in both USB plugs at the PC end of the cable, (you need to do this so the external drive has enough power), before you connect the drive ?

Also, motherboards with VIA chipsets are well known for not being able to supply full spec power to the USB ports.  Any idea what make/model yours is ?

Dumb question, have you tried all the USB ports ?

The fact that previous and current external HDDs are having this problem points squarely at the PC as being the cause.

Have you reinstalled the system between the time when it first occurred and it's latest occurrences ?

If you have, then unless it's specifically related to a piece of software you keep installing it's more than likely a hardware problem - either the motherboard or the USB ports themselves.

[Paul Keith]

Oh, I didn't know that. I've replaced the two usb plug with a single usb one thinking the other one was just an extra plug. Thanks. That could be it.

Two XPs as in separate HDs but similar machine. Hmm... I wonder if I should re-build a new PC again. I've been told that could be the problem before but it's so sporadic and I have little knowledge of how to build a cheap PC, I kept prolonging and prolonging it over and over again.

[4wd]

Oh, I didn't know that. I've replaced the two usb plug with a single usb one thinking the other one was just an extra plug. Thanks. That could be it.

-Paul Keith (November 23, 2008, 09:14 PM)

Another post I made regarding the power usage of external 2.5" HDDs.

You should always use the cable they supply, always plug in the PC ends before the HDD and never plug them into an external USB hub unless you know for a fact the hub has it's own PSU.

[Paul Keith]

Thanks, I just read it and am going to save it now. Do you recommend USB hubs with their own PSU as a cheaper alternative to new pcs though?

Edit: btw those are some advanced stuff. Do you have any recommendation for learning voltages with a degree?

[4wd]

Thanks, I just read it and am going to save it now. Do you recommend USB hubs with their own PSU as a cheaper alternative to new pcs though?

-Paul Keith (November 23, 2008, 09:28 PM)

That would come down to whether you want the extra grunt of a new PC or just want to update your current one because it does everything you want.

A self-powered 7 port USB2 hub, (external), costs AU$15 including the PSU.
A USB2 PCI card is AU$10.

A lot cheaper than a new PC.

Edit: btw those are some advanced stuff. Do you have any recommendation for learning voltages with a degree?

With reference to Australia, (and the mid-1980s), you were able to do Certificate Of Technology (Electronics), there's also Bachelor Of Science (Electrical Engineering) as well as others probably.  They've probably undergone a name change since I went through the penal educational system though.

To be honest, I only ever did the first 6 months of C.O.T. Electronics then got a job with, (then), Telecom Australia, but I've always had electronics as a hobby since I was about 12 - so with regard to general electronics knowledge I'm basically self-taught.

If you're interested there are a few online resources to get you started, (haven't looked at any of them), like this one.

Second thoughts, forget I mentioned that one   I'm sure you can find plenty using Google, or just go to the local library.