Microsoft has today revealed details of an upgrade to Windows Phone 7 at the Mobile World Congress.

Not content to sit back and bask in the potential of last week's Nokia deal, Microsoft CEO Steve Ballmer presented details of changes to the Windows Phone 7 coming later this year.

The significant changes in the free update will include copy and paste support, multi-tasking, the addition of SkyDrive support into Office for Windows Phone 7, native Twitter integration, and a version of Internet Explorer 9 for the device.

An early build of the Windows Phone 7 update was demoed during the keynote, with some interesting additions clear to see. Multitasking, in particular, looks slick, with near instant switching between apps using the Start button. Multiple running apps can be browsed by holding the Start button, then flicking through the previews of the open apps.

An interesting point to note is that the new multitasking will support third party audio applications. Windows Phone 7 users will be able to tune into radio apps while using other programs on their phone.

Internet Explorer 9 for Windows Phone 7 was also shown. Its support for graphics hardware acceleration was demonstrated by running the IE fish task test through a Windows Phone and an iPhone, with IE9 delivering a significantly smoother view of the fish, even with more fish on screen at once.

Another highlight of the demo was a video showing an early build of Kinect support for Windows Phone 7. The example given was a bowling mobile game, which is controlled by linking the phone up to the Kinect.

Steve Ballmer, predictably, was a little excited about the new update, saying: “Windows Phones are now the easiest to use and most delightful phones available”.