PB622 : library reorg, access, etc

I have taken possession of the new toy, and have a couple of beginner questions:

1. The library has quite a few folders and/or books that do not interest me in the least. To save space and simplify things, can I simply delete them?

2. If I install a micro sd card, how will it be mounted by the system?

2. It seems that anyone can power on the device and have access to the whole contents, since no userid and pwd were required. In the pc world, being a Linux user, I was not a little surprised. Any hints?

Thanks in advance for help.