Katy Perry Performs Free NYC Concert For Windows Phone 7 Launch (PHOTOS)

Microsoft released on Monday three devices built on its new Windows Phone 7 platform.

To celebrate the launch, Microsoft and AT&T hosted two free concerts, one by Katy Perry in New York and one by Maroon 5 in San Francisco.

The Huffington Post attended Katy Parry's show at the Roseland Ballroom, where the pop princess drew a large crowd of cheering fans. Minimalistic Windows Phone 7 displays flanked a stage bedecked with oversized candy canes and lollipops. Perry made her entrance by jumping out of a giant cake while confetti rained down on the audience.

Dressed in a latex mini dress, the California Girl joked about embarrassing Facebook photos and told the audience to download the title track off her recent album "Firework." "Download it on your new Windows 7 Phone," she suggested.

View our slideshow below to see highlights from the performance.