USB History Viewing
You can view a history of USB devices plugged into Windows systems (Windows 2000/XP/2003/Vista) by using USBDeview.
To do this, extract the SYSTEM file from c:\Windows\System32\config (or equivalent path.)
You can do this indirectly via Encase or any other system imaging format/type (.dd, .e01, etc) by extracting the "SYSTEM" file from the image to a local path.
Once this is complete, open up a command prompt and run USBDeview. Example:
usbdeview.exe /regfile "c:\case number\system"
This provides information including the device name, description, last plug/unplug date & time, serial number, etc.