Yes Win7 would need you to load drivers for the usb3 chipset as it doesnt support USB3 natively. You should be able to see it in Device manager.
Just because your case has usb3 ports doesnt mean they're connected to anything.
I'm afraid you'll need to open the case and check that.
as a test you can plug the Sandisk drive into a usb2 port and it should still work, just at reduced speeds.