They can probably be easily accessible because your username and password are the same on ubuntu.
Back to your windows machine.
Navigate to Computer Management
, Right Click on Computer
(You might have to accept UAC prompt)
Once Computer Management opens you will want to focus on the left
Select Shared Folders
From here you can see everything that's being shared on your PC.
From here you can do 1 of 2 things. You can right click on the share and choose stop sharing, or you can navigate to each folder and stop sharing.
The (DriveLetter)$ "DriveLetter" are hidden shares created by the system for administrative purposes. Keep them, remove them its up to you.
the IPC$ is a whole different story though. I would just leave that enabled, more information below. Description of the IPC$ share | File Sharing | Smallvoid.com
More on hidden shares: http://support.microsoft.com/kb/314984