I may be able to help. When you installed Spybot S&D, did you check the box which lets you scan from the context menu in Windows explorer? If so, you should be able to go into My Computer, and right click on the harddrive, and run the spybot scan from that right click menu.
If you do not have this enabled, there has to be another way. But I looked in the settings of Spybot and couldn't find a way to configure it to scan other drives. But maybe I didnt' know where to look.
To get the context menu scan capability, you could, uninstall and reinstall spybot, and then make sure you enable context menu scans this time. But you should only do that if there is no other way to get it to scan I: drive.