how do I Block Installs in a PC.

Is there a way to restrict software installs in a particular PC,
something like the thing they do at some offices so the employee wont be
able to install just any program;, except that this PC is not part of a workgroup.
I don't know if there is a way of doing it within Xp,
or may be a 3rd party app.
tnx guys.

I am not very experienced with this. Therefore, if it is wrong, then please excuse me.

I think creating a limited user account would help. Limited users can't install anything. It can be created from Control Panel > User Accounts.

just install vista?