If you can't get the Kobo to appear as a device in Windows, the only other means would be to copy ePubs onto an SD card and use that.
When you mention unable to eject, I wonder if something (for instance an antivirus) might be scanning the files on the device?
If you are up to it, there are some tools from a web site
http://www.sysinternals.com that could help see what has the device open.
For instance, the tool Handle
http://technet.microsoft.com/en-us/s...rnals/bb896655 can show what programs have a given drive open.