Windows XP Pro Group Policy (I think)

Hello everyone I'm just looking for any help on how to setup a group policy on Windows XP Pro local machine, which affects just one user, and not the administrator, for enabling a single local user to be able to download and install software.

Do I need to be using Windows 2000/2003 Server (AD) to do this ?

I know how to make the user an administrator and also how to use the RunAs command but that is not what I need help with.

Thanks