I got this installed in a VM just now. I'm going to assume that you used the default settings.
Subversion Install Directory:
C:\Program Files\CollabNet Subversion Server
Command-Line Tools Directory:
C:\Program Files\CollabNet Subversion Server
Repositories:
C:\svn_repository
Remember that this only works with svnserve and not Apache. I haven't actually tested it with SVN Backup Widget yet, though. The way CollabNet installs stuff is a bit spastic, and I haven't tested this setup with any of my Subversion tools.
Please do let me know how this works for you. Had a very long day today (work, snow, and life in general) so I'm going to bed early.