[drummerguy101]

I've had a 500GB Maxtor Basics External hard drive for about a year now and I've just bough a 640GB Maxtor Basics External Hard drive.

They are both working fine when they are plugged in alone
the problem starts if I try to have both of them connected to my PC together, the second hard drive that gets plugged in (doesn't matter which one it is) gets "USB device not recognized or has malfunctioned"

I tried changing the drive letters, the 500gb to "Z:" and the 640gb to "Y: "
I also tried changing the USB sockets they are plugged into but they still dont work together.

also since this error started my 500gb hard drive displays "Total size 500GB" in Windows Explorer but if I go to "Disk Management" it says its "595GB"
How can a 500GB hard drive show up as 595GB?



What do I have to do to get both Maxtor drives connected to my PC at the same time?




also the 500gb drive sometimes displays an error about "Delayed write failed
I have included a screen shot of the message

[Alex Ethridge]

Are you using a USB hub or USB add-in card that both drives are connected to? Sometimes certain devices connected to the hub or add-in card will interfere with each other. Additional info: Add-in cards with several ports sometime seem to function similarly to a hub, in that hubs sometimes allow conflicts between certain types of devices.

Try connecting one hard disk to a port on the front of the machine and the other to a port on the back. Let us know your result.

[drummerguy101]

Thanks for your reply

Im not using a USB hub, I'm plugging them directly into the sockets located on the machine.

I have tried connecting them like that, with one drive to a socket on the front and the other to a socket on the back and I get the same thing.

[Elvandil]

I actually have never seen anyone succeed in connecting 2 external hard drives to an XP machine. The problem you describe is widespread and may be a function of the board or OS. You'll probably need to use one at a time. I couldn't use 2 even when one was connected to a completely different add-on PCI USB card.

[fairnooks]

You must mean 2 external hard drives of similar make maybe? Cuz I've got 6 externals connected to one XP machine, 3 or 4 of which are on an add-on PCI card. I also have several instances of two externals running on one XP machine, all with absolutely no problem.

I did have a similar error once on one system, in this case XP home, with three externals connected but two work fine.

In this case it looks like the recognition protocol is so close or identical between the two drives that the system cannot distinguish between the two. Possible confirmation of that is the 500 gig showing up as 595 in disk management, the proper formatted size of the 640 gig drive.

There's a program that blows out all the old logs of all the USB removable storage devices that have ever been plugged in, maybe someone can help with the name or I'll find it sometime. Fresh recognition might do the trick or not depending again on how similar the two drives actually are. Might not ever work.

The delayed write can come up for a couple of different reasons, one of which can be remedied by checking the drive properties in Device manager and if its set under policies to optimize for performance, check the optimize for quick removal instead. Maybe even delete the USB drives listed there, reboot and plug the USB drives back in again and see if that helps.

[Noyb]

Just a wild guess .. Are each of these running the one touch backup software ??
I can connect several Externals to any of my several XP computers .. No Problem...

[Rich-M]

This has been an issue for years and no one really knows the answer but it definitely is hardware. I noticed it ocurred loess with Vista and especially with pci-express cards and there could easily be a situation where similar or the same drives causes it as well, there has never been an intelligent answer. I have always used a 1394 and a usb if I needed 2 for that reason because 1394 can have the same issues as well if 2 used.

[Elvandil]

Yes, it is a prevalent problem. I'd say that in the last 6 months, at least 20 people have asked me why they couldn't use more than one drive at a time. On the 3 machines I have in the house, I can't even use a USB CD burner if I have a MyBook attached, too, in either Vista or XP.

There is a registry hack (actually a new environment variable) that will allow Device Manager to show all devices that have been attached and that it has stored data about. But the easiest way to remove those entries, as fairnooks mentioned (and I hope she finds an automated way to do this), is to use USB Device Viewer. It shows all devices, past and present, and allows you to remove all the old entries, especially all those "Unknown Device" drivers that have been loaded.

[drummerguy101]

I tried connecting both drive at the same time to a friends PC and they both work!

both of the drives are exactly the same Brand\Model - "Maxtor Basics", but they are different sizes, a 500GB and a 640GB

I do not have any one touch backup software installed because they are not "one touch" devices just basic.

[Rich-M]

They may both get recognized but usually after you access one, the other is not accessible but again not on all systems.

[Elvandil]

At least 2 of my systems that do that have VIA chipsets. No idea if that has anything to do with it, but clearly different people are having different results. The fact that VIA is so common might also explain why I have never seen more than one drive at a time in daily work.