Most likely it depends on the outer box maker. I use this Philips on the image below, it does power down with other USB tools, including Vista's built in, but you wouldn't know, would you?
Somewhere in 2006-2007 Philips launches the World's First 1TB External HDD, I bought several ones at once, some of them where upgraded to another HDD sizes, like 2TB, but the boxes are the same, made by Philips, all aluminium.