|If your install was correct and XP identified the bios ability then you could enable hibernate.|
Hibernate would power down after so many minutes but it would also make it faster booting back up. It saves your desktop and then powers down.
You could set all your computer stuff including wall warts on a power strip and actually press the power button too. It would secure your system from lightning and save energy.
"Best Practices", Event viewer, host file, perfmon, antivirus, anti-spyware, Live CD's, backups, are in my top 10