Sharing Folders and Disks - Unsharing external USD drive

I do not find any information on what physical hard drives of my host OS are shared by default and how I can change that (Mac as host to XP virtual machine).

The problem is this: I did not share the external USB hard drive (which is the backup drive used by Time Machine) of my Mac to my XP virtual machine. However, it is there as an "object of the network neighborhood" (as you call it in your documentation). And I do not want this happen - meaning I want to revert this.

The situation looks like this:
From the VM level
- The external hard drive appears as a psf-drive listed unter network drives in My Computer and is accessible
- The same drive does NOT appear in the folder Parallels Shared Folders

From the Configuration menu:
- "User-defined Mac OS X folder" is checked, and which lists a folder of the internal hard drive of host OS X
- "Share Mac OS X folders with Windows" is NOT checked
- USB Controller: NO USB devices are connected

Again, how do I make the external USB drive to be NOT integrated with my VM? It is especially puzzling, since it is stated under configuration that NO USB devices are connnected.

 

The situation you describe seems to be the effect of a SmartMount feature. You can check what it is at the following link:
http://download.parallels.com/desktop/v4/docs/en/Parallels_Desktop_Users_Guide/27561.htm
In short, any USB device connected to the Mac will be also mounted as a network drive to the virtual machine. The feature was implemented to make it easier using the same USB device both in host and guest OS.
If you do not need this, you can simply disable the feature.