The default behavior for USB is for the host (upstream side) to connect all devices (downstream side) at the maximum speed the device will allow, with no regard for what speed you may actually want to use. IOW, the default connection speed is determined by the device, not by the host or by what you may want to happen.
However, if you have older hardware, which has both high-speed (EHCI) controller(s) and full/low-speed (OHCI or UHCI) companion controller(s), it is possible to "shut down" a specific EHCI root hub port. This will force all of the devices attached to that port over to the full/low speed controller. This is something that specification-compliant hardware allows, but I don't think Windows supports the use of this feature (some other OS's might). You should also be able to disable/unload the EHCI driver, which will effectively force ALL of the ports off of the EHCI controller and onto the companion controller(s) (never actually tried it myself, but it should work).
Remember, though, that this will only work if you have older hardware which uses OHCI or UHCI companion controllers. Newer hardware generally doesn't work that way any more, so you MUST use a device that will only connect at the speed you want it to. Inserting a USB 1 hub upstream of a device is an indirect way of ensuring it cannot connect at high-speed.
