Regular Zune users may have already noticed the alert warning of some impending downtime, but those that haven't should know that Microsoft is advising folks that some maintenance scheduled for tomorrow could last for as long as 24 hours. That will begin at 10PM PST on January 25th, and will affect all Zune services, including Zune Pass, Zune Marketplace, Zune.net streaming and Zune video on Xbox Live. Once the service is back up, users will also have to update their PC software, and users of Zunes other than the Zune HD will also have to update their device's firmware. This scheduled maintenance is also apparently just that, maintenance -- although Microsoft is promising that things like Smart DJ and other features announced at CES, as well some as "unannounced features," will be rolling out in another update sometime this Spring.