@martin: was your xbox previously banned from going online? because getting banned puts a flag in your profile that corrupts it when you use it on another box or, in your case, switch to another hard drive. at least that's what i'm guessing. you could probably use the con flag remover utility, and then the hash block calculator to fix it. Unless there's an entirely different reason for corruption.
boy, is my face red now. I went to the windows Action Center to check UAC settings. And they were set to the lowest (I'm pretty sure that means off, the bottom of the slider), then when I clicked ok, it was telling me to restart, although I hadn't changed anything. When I restarted my computer later, I was suddenly able to drag-and-drop into our fine program...... go figure? Ah well, all's well now! So your fix did work, icepir8icepir8. I guess "you're doing it wrong" applies to all those who it's not working for under win7 x64.
All my problems are solved now.