Realation between Guests and Users groups

Hello,

I may have a trivial question.

The Guests group should be much more restricted then the Users group,
according to documentation. However, I tested this on my computer (WinXP
SP3) with a user that is in the Guests group but not simultaneously in the
Users group. The user seems to have the same privileges as if he were in the
Users group. (I.e. I can see and modify files, execute any programs
including internet browser etc.)

In particular, on my hard disks I never have privileges specified
explicitely for the Guests group. But the user obtains the rights that are
specified for the Users group. As if the Guests group was a member of the
Users group (but it is not).

So, what is the relation between the Guests and Users groups?

My system is WinXP Pro SP3 with default security settings (i.e. I have not
modified the privileges on disk folders nor the hierarchy in user groups).

Thank you,
Martin.