changing default custom scan, Norton Antivirus 10.1.5.5000

I never used to have this problem but recently my Norton Antivirus has
decided to pre-chose certain directories and files as default for the
"custom scan". I use the "custom scan" all the time for individual files
that I want to check, but I want it to start with a blank slate. As it is,
I have to first uncheck these pre-chosed directories/files before I check
the one file I want to scan. When I forget to do this, I end up with a scan
that takes hours instead of 30 seconds.

I've been looking for a way to set the default for the "custom scan" but I
haven't found it. Does anyone know how to do this?

jc