In order to delete your application history in Windows 8 Consumer preview, go through the tutorial below.
The Application History stores the log for all applications in Windows. You can delete this history quite easily in Windows 8 Consumer
This tutorial will guide you to that way. Follow the instruction carefully.
1. Press Windows + I to open the sidebar and then click on More PC settings.
2. In the PC Settings, switch to the General tab. There you will see the Delete History button
under App Switching. Click on this button to delete application history.
3. After successful completion, it will show a messege “Done!” on the right side of the Delete History button.
You will also observe that it not only delete the application history, but also close open switched applications.