Windows Security Update installs as Power User

We would like to deploy WinXP SP2 and Windows Security Updates to multiple WinXP computers however our users are restricted and only have Power User rights.
We are interested in perhaps a group policy that can be implemented locally that will allow Windows Security Updates to be available for download and perhaps automatic installation. Our network environment consists of both domains and small remote workgroups. We do have vpn tunnels to every office.
Most likely we do not have the time or resources to deploy SUS or any other patch management solution.
Is it possible to install Security Updates as a Power User?
How can we enable a Power User ID for automatic Security Update downloads and installations.
Looking forward to your response. Thanks.