virtualbox.org

Google for Intel xHCI drivers, install, done. That's all you need to do.

The question about Parallels was why you think your experience with Parallels is relevant here. Parallels is not VirtualBox. And no: I use VirtualBox, plus I have a Windows host, so it cannot be assumed that I am familiar with what Parallels has or doesn't have. I can tell you that the fact remains that Win7 does not have native support for xHCI. How could it? Your Win7 installer is older than xHCI. And this fact is as true for Parallels users as for us, so I'm not entirely sure what you think was working there.

Thank you! Especially for dealing with dummies like me. I would have never known to search for xHCI driver. I have no idea why Windows 7 found it on the Parallels install. But again thanks!

Parallels must have done something.

All I know is that for reasons that aren't entirely clear, the Intel xHCI drivers (or NEC/Renesas xHCI drivers for that matter) are not on Windows Update and must be installed manually. It may be Microsoft policy, their position being that if you want to use USB 3.0, you should be on Windows 8 or later. The newer Windows versions have the support built in.