Not all questions are simple in these forums.
You could just create a single "demo" account for people to use and try out ...
This is a very old post, but I thought I would add something that might help. Actually, I have a course that is set up for users that is sort of like their own "personal page". (They go there to use the dialogue, post assignments, etc.--there are no discussions.) So, to make it look more personal, I have hidden the participants block altogether. If someone wants to edit their profile from that page, they can always click on their name (in the upper and lower right corners of the page).
I know this is a very, very old topic but I'm intersted in the same question.
To answer Martin's last question - "Why would you want to hide participants?"
My courses are for corporate learning. We sell a product that is new in the industry and companies aren't ready to let their competitors know that they are investing in our products. They feel that if their competitors know, they won't have the "leg up" on the competition.
So I'd like to allow for people from company X and from company Y to be part of the same course, but I don't want any of them to know who else is in the course. This means that we won't be able to use the forums, but that is not an issue for us.
This would be a good question in the Using Moodle for Business course. In the latest version of Moodle, the Participants link is the only thing in the People block, so just hide that block. Then, set up the course with separate groups, giving each group their own enrollment key. Then they won't "see" each other.