I share you some my experiences with the external USB disk.
The external USB hard disk is simialr to yours: IBM 30GB, 2.5' (for notebook),USB connection case with USB 2.0 interface (bought in April 2002).
My notebook: Toshiba satillite 2650 (very old model, bought in 2000), with USB1.1 (maybe 1.0), Win 98.
When I bought the hard disk, and connected it to the notebook after installed the USB driver, the notebook said: unknow device. so I brought the hard disk to a friend with a desktop (Acer,win2k).His machine recognised it and formated it for me. Then I took back the hard disk and connected to my notebook again, the notebook recognised it: 27.9GB. When I copied file into the disk, no problem, but when I tried to delete something on the disk, machine halted, then I had to restart. Several times. Then I brought to the desktop again, it works very well, no problems with any operation(no need to connect PS2). There is a line from the middle of the USB cable with a PS2 interconnetor. After connected to the PS2 to my notebook, the disk works well on my notebook.
When one of my friend asked for some my files, I brought the disk to him. But the disk did not work,always: 格格”的响.His machine is: compaq notebook, win2k, even connected the PS2 port. I don'k know why. Now, I have a compaq desktop, and when I connected the disk to the machine, it also does not work, just"格格”的响,even does not recognised it.
After discussed with another friend, he said all japanese notebooks are designed to save power and the power output of USB interface is very small (how small I don't know). But why compaq computer (notebook and desktop) don't recognise the extertal harddisk? I don't know.
My personal opinion:
1. if notebook does not receognise the external USB hardisk, it does not mean that the disk is damaged.
2.Power consumption of most USB case (IDE to USB interface and hard disk, 2.5') is higher 500mA x 5V (standard is 400mA x 5V).
3. For all notebooks, the connector to PS2 from the disk should be connected (or the disk has external power supply).
4. Compaq (maybe include HP) does not recognise this hard disk.
