Sprint rolled out Android 2.1 for the HTC Hero, but with one important caveat: Installing the update will delete all the data and information  from the phone.

In a note on the support page for the device, Sprint said users will lose contacts that have not been synced to an email account, text messages that have not been forwarded, saved voicemail messages older than five days, voicemails older than 20 days that have not been listened to and call history. The calendar and email settings also will revert back to factory defaults.

Sprint also told users to remove the device’s microSD card before updating the phone, though HTC said on its website that pictures, video, music and other media saved on the microSD card will not be affected by the update.

The new software is not being installed through an over-the-air update; users must connect the device to a computer with a USB cable to download Android 2.1 through HTC Sync.

Some of the lost data can be recovered if users have synced with phones with an email account. Text and multimedia messages have to be forwarded to an email address for backup and applications will have to be re-downloaded.

The HTC Hero had been running Android 1.5 Cupcake; the upgrade to Android 2.1 Éclair marks a significant increase in the number of features supported by the operating system.

The upgraded HTC Hero will have support for Microsoft Exchange, built-in support for Flash and HTML 5, search functionality for all saved SMS and MMS messages, improvements to the device’s virtual keyboard and double-tap zoom.

Sprint said last September it would launch the HTC Hero. Wireless Week reviewed the device after its release.

The Hero features a 3.2-inch touchscreen, a 5-megapixel camera and 32 GB of expandable memory through a microSD card. The device also comes preloaded with the HTC Sense user interface, which adds on additional functionalities, including aggregated social media feeds.