Drupal's multi-site feature needs symbolic links to point to the directory where Drupal's core code resides.
There's a tool installed within Windows 7 that allows the creation of a symbolic link, called MKLINK.EXE. It works in a similar fashion to ln under linux. Here is an example of how to use it:
c:\> mklink /J c:\drupal\sites\neubreed.com.au c:\mysites\neubreed
This will create an invisible "shortcut" or fake directory "neubreed.com.au" in c:\drupal\sites\ that magically points to c:\mysites\neubreed