My old emachines pc with XP has a WD Mybook usb external drive. It has been working fine. The pc has usb 2.0. I am now getting "hi speed usb device connected to non hi speed hub" and the data rate is low, about 60MB/min.
I have uninstalled all usb drivers and allowed XP to reinstall. Tried updating usb drivers in Device Manager - all up to date.
I had a problem a few weeks ago. I installed an update of a registry cleaner. The old version was fine but the new one deleted a bunch of things it should not have. Had to reboot to last good configuration. After getting running, undid the registry cleaner changes from its backup. PC has been fine since until I noticed the usb for the WD drive was slow. May or may not be linked.
All service packs and updates installed (except IE8). Presently only the mouse and external drive are usb-enabled.
I tried connecting my old external drive but had similar problems. Both drives could copy to the internal drive at about 16MB/s. However, when trying to write from the internal to external drive, the "hi speed usb device connected to non hi speed hub" appears and the drive disappears from Explorer. I also had the WD Mybook asking to install software to run it - it's plug n play. It was also listing itself in Device Manager at times as an "Other" drive.