Although I am not currently working in a museum I do work in a plave
that offers public access to the internet. This is how it works.

Persons have to sign in, but do not have to book.

Usually we ask them what they are searching for.

The majority use it for email - especially the tourists.  It provides
them an easy and cost effective way to keep in touch with family
members back home.

We have had no problem with the tampering of programs etc.

We do have seperate security on each computer.

We log the user on to the computer.

If we believe the person was doing something on the computer that
they should not, or to see what the interests of the clients are we
can do a internet history search. This allows us to see what sites
they visted and how long ago, how many times and through the search
we can go into the site .

As a note: I think that it would be great to have this in a museum
since it would provide another reason for people to go and continue
to go. Therefore, they will become a custom to seeing all new
exhibits, lectures, workshops etc.

Good Luck with you project.