It would need power management circuitry in the external drive itself (on the interface board). I don't think it's possible

Hi Smash, smarty pants, because I don't want to crawl under my desk all the time. But if there is no PC solution I might get one of those "remote switches" from Home Depot.
@ Lighthouse, But there must be some switching capability since it switches off when I go into Sleep mode. I wonder how Sleep mode does it. And it powers it on when you come out of sleep mode.

Yes Lighthouse, I tried that too. But it is the same problem. I have to crawl all the way under my desk to do it and then again to plug it back in. At my age I try to keep the gymnastics to a minimum. I think I'll get myself one of those remote electricity switches at Home Depot. They work well with some other application in the house. But I am still puzzled how Vista does it when you go into and out of sleep mode. They must control it with programming. I have also tried "safely remove" but that was no good either. I know that the power is cut off from the SD card reader if you use "safely remove". But then you have to Restart Vista to get it back. Can't win. Btw: For SD cards one should use EJECT. Thanks anyhow for experimenting on my behalf.

"At my age I try to keep the gymnastics to a minimum."
4 out of 5 Dentists recommend The Clapper ;)

http://www.amazon.com/Clapper-.....B0000CGKLR

@ Lighthouse, I banned it "far away" because i did not want to be bothered with the additional noise and my desk is kind of crowded already.
@ Scott Those Clappers are ok, but I think the once that are controlled with a certain frequency signal work even better. I have a couple to control lights.

Thanks for the idea, Lighthouse. It allows me to power on and off a disk in an external USB enclosure. First thing I did in the Device Manager was to find the disk under Disk Drives, right-click for Properties, select the Policies tab, and configure it for quick removal. I assume this is important, if the disk is to be forcefully switched on and off. Then, under USB controllers, disabled / enabled the USB Root Hubs one by one, to find the one controlling the disk. The disk should not be in use (for example, open in Explorer); if it is, trying to disable it causes a prompt to restart the machine. Having found the right Hub, I right-clicked it for Properties, selected the Details tab, and Hardware Ids in the drop-down list. In my case, one of the ids ends in PID293A. The following DevCon commands can therefore be used to more conveniently disable / enable the Hub. Storing these commands in .bat files, shortcuts can be created to run them. Maybe there are better ways to go about all this, don't know. DevCon is available from MS.
devcon disable *pid293a
devcon enable *pid293a
http://support.microsoft.com/?kbid=311272

Well, I've just realised that this actually disables a whole USB Root Hub, which disables not just the desired port but also a few more. Will post a solution, if I find one. But maybe this is just how it works: the device seen by the system is the whole hub. If so, then I guess wasting a hub with just one device is the price to pay for the convenience of powering it on and off without physical intervention...

Thanks - I tried that, but what then happens is that the USB Root Hub in question is reassigned to a different controller, so the disk is re-detected and stays on.

Ok, here's what worked (actually, don't know why I didn't try this the first time, because it was the most obvious option!). In my machine at least, under USB controllers, besides a number of USB Universal Host Controllers and USB Root Hubs, there are also a couple of USB Mass Storage Devices. One of them is the external disk and can be disabled without affecting anything else. Thanks again for pointing out the Device Manager!

jd, see my last posting above answering to Lighthouse. This is not really an option for me. But I think I will go with a remote switch from Homes Depot. Don't want to disable a hub. Have too much stuff.