When running VirtualBox with a Windows XP client, I ran into a problem where it worked fine before I installed the Virtual Box Client Drivers, and then, any mouse movement resulted in the mouse pointer moving slowly down and to the right. It turns out this is a known VirtualBox conflict with the SMS mouse driver. (SMS allows the Windows domain managers to manage your PC, including remote control.)
So I uninstalled SMS. Problem NOT cured.
So I checked Device Manager. SMS Mouse Driver does not appear.
It turns out that there is a Microsoft known problem, where uninstalling SMS does not uninstall the SMS Mouse and SMS Keyboard drivers. But why weren't they listed in Device Manager?
Because SMS had been uninstalled the 'devices' no longer existed, and Device Manager doesn't show non-existent devices. The solution? See Device Manager and Invisible Devices elsewhere on this blog. Then delete the SMS Mouse Driver and reboot.