The design team behind the shock family (iconshock, webdesignshock and themeshock) have created a complete set of GUI elements inspired by the new windows 8 interface, called Metro.
It was made purely in Photoshop using vector shapes, so it will be easily adaptable to your design changes.
It contains more than 100 GUI elements for windows 8 (PSD)
This great set is included in a single but perfectly organized PSD file, with separated layers for each screen, each element has been carefully designed, checking off every single detail.
Some of the included elements are:
Here are a bunch of samples from the graphics pack.
You can click on each graphic to see it full sized.
You can download the set for free here