I have gone through many different remedies and cleaners to help in keeping Windows free of infections, virus, trojans, root-kits, etc.  SuDown is designed for Windows XP, it's free and is by far the most effective and easy to use solution. 

 If you don't have one already, give your User Account a password to get started.  Download and install suDown.
SuDown creates a Limited User Group called "sudoers".  Reboot the computer and sign in with your password.  Right click on the Desktop and you will find the entry:  "# sudo Control Panel"
When you click on it, it will inform you that you need to be a part of the sudoers group to use the sudo program and would you like to add this account to the sudoers group.
Click "Yes" and you're in.

No pop up allow/deny ~ dark screen notifications like in Vista.   A simple, you don't have permission dialog is the reminder. Right clicking, choosing: "# sudo <application>" gives administrative permission to the application and it can be run.  For example:  defraggers need administrative priviledges, so right click on your defragger and choose:  "# sudo <defragger's name" to run it.  Check out the following links for more information and to download.  Be sure to watch the video demonstrations as well.

suDown sudo for Windows XP

suDown Video Demonstration

Download suDown