Preventing access to software and user on laptop

[John]

Hi,
I would like to know URGENTLY how I can do the following:

1. How would you lock a laptop, preventing end user use,
when it is running either Wind 2000 or Win XP?

2. How would you prevent a user from running specific
software on a laptop, and how could you prevent them from
loading specific software from the internet onto a laptop?

Thanks for the answers.

John