I know this is marked solved but if I may add a couple of comments. Here is the documentation on dealing with themes in the browser address window,
http://coppermine-gallery.net/demo/cpg14x/docs/index.htm#creating. To address the problem with someone typing in the theme as per the above instructions, what I did for a friend was add a single character to the theme folders except for the main theme that was left as normal. Examples are:
classic
hardwired1
mac_ox_x1
reynolds1
etc...
The idea here is that by leaving the main theme untouched (in this case, classic), no one would know what the other names are. Adding the same character to all the themes makes it easier to rememeber. When someone tries to change the theme and it doesn't exists, CPG will cough up the admin selected theme. The reason for not just removing them was that he's working on developing themes and doesn't want to upload them all the time. This way only his selected visitors will know what they are (I'm one of theme!
).
While I do use the PayPal hack, I try to avoid hacks because you have to remember (and document) what you changed and when upgrade time comes, you may have a lot of work on your hands especially if you have a lot of themes to upgrade. Plugins are most cool because all you have to do is upgrade the plugin and all is well again and you can turn it off very easily if it fails or you need to for other reasons.
Just my thoughts on the subject.
Cheers,
Gizmo
PS. Hacks are a good thing but if you are a very dynamic person who likes to make a lot of changes to your site or themes, hacks can make more work for you and may even cause you to lose interest because of all the work involved.