MYSTERY ON USB EXTERNAL HD

On a Windows XP Pro system, I have a problem with a single USB ext HD enclosure and/or its HD. All other enclosures of the same model used on this system have no problems connecting to, or functioning with the system.

1. When a USB data cable is inserted into this USB enclosure, the Windows XP Pro system brings up a USB icon in the tray area, but recognizes only a drive letter from Windows Explorer / My Computer. Windows Explorer believes the USB ext HD is not formatted.

2. Not only that, but increasingly often, the system will not recognize the USB ext HD enclosure after data cable is inserted. On such occasions, no USB icon appears in the tray area and no drive letter appears in Windows Explorer. However, after data cable insertion, the USB icon sometimes spontaneously reappears after a few minutes, but the USB device still does not appear in Windows Explorer. I have exchanged another known-reliable USB data cable, but with the same results.

3. When the HD is removed from the USB enclosure and installed on the IDE primary, Windows Explorer can see the HD with volume name and all files, seemingly intact. When the same HD is returned to the original USB enclosure and a USB data cable inserted, the old symptoms return.

4. When a drive with no (known) problem is installed in the original enclosure, all normal functions return-- Windows Explorer not only recognizes the USB ext HD enclosure with a drive letter, but its volume name and file structure, as well.

Clearly, a data structure critical to USB operation is missing from the original USB enclosure-mounted HD. I have reviewed countless forum posts, but most address boot drive issues, and the relative few that deal with USB ext HDs are usually resolved with mounting the drive to the IDE primary. A few more cases are resolved with chkdsk /f in safe mode, or by running the recovery console with the "R" option on a boot drive.

But I am supercautious about running chkdsk with any switch, since chkdsk mangled data earlier on another HD when the system attempted a chkdsk run automatically to "fix" the volume.

The mystery is simple to define-- if a data structure (MBR, index, FAT, etc.) is missing from the USB ext enclosure-mounted HD, why is the same HD recognized with no apparent problem when installed on the IDE primary? (Of course, the HD is jumpered to master in both cases, with the second internal IDE slaved).

What data structure appears to be missing? How is that structure restored safely and reliably?

Some USB controllers don't like certain drives.

Try that drive on a different model enclosure, if it is doing this across several enclosures with different controllers then there is likely a problem with the drive.

when you boot your PC with the drive on the IDE does it hang at the bios a little or does it boot clean

It may help to identify the USB-PATA bridge chip inside the enclosure, then search for known issues with that chip.

If your enclosure is a generic one, then you can use Microsoft's UVCView utility to identify the bridge IC:
http://www.users.on.net/~fzabkar/USB_ID ... ew.x86.exe

Otherwise read the part number of the largest IC, probably in a square package.

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fzabkar-- this is one possibility, since the enclosure was manufactured years back, but it would not account for inconsistent HD behavior in and out of the enclosure (1) if another, known good drive behaves properly inside the enclosure, and (2) the suspect original drive has no problem as the IDE primary. Thanks for an interesting perspective.

moinstermunch-- no noticeable BIOS hang, and I am accustomed to a full, verbose display at boottime, so I probably would notice, if there were delay. As I recall, instead of a delay at boottime, I was impressed at how quickly the system adapted to my swap of IDE primary HDs. Good conjecture, though, since a faulty HD should have misbehaved as IDE primary.

Russ-- You suggest, "Some USB controllers don't like certain drives... Try that drive on a different model enclosure..." This would be logical, if the same (model) drive always had suffered problems with the system and its USB stage. But performance was always OK until one day I either bumped the USB cable, or in some way disturbed the tenuous data connection, and things never have been normal with this drive since then. My theory is what damage was done to the data structure was done then, but what the damage is, I cannot determine yet.

HERE IS THE DEVELOPING STRATEGY-- Move all data off the HD onto another HD. With the original HD as IDE primary, do a zero-out of every sector, using SeaTools DOS. Using SeaTools DOS, reset the HD native capacity to 250gb, partition and format, and followup with a good surface check with SpinRite 6 at level 5. That will take a whhile, but all the problems will be removed-- if the problems are data-related.

And after that, never, ever touch the USB data cable during USB ext HD operations again. Since I brushed the USB cable inadvertently with my knee, this event is less likely to recur if I shut down all USB externals when not in use as a backup device.

I've bin'ed that enclosure!

Bosse

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