Windows 8 (Developer Preview) Metro Tile Apps don't open

If your Windows 8 dev preview Metro apps refuse to open the most likely reason is that your screen resolution is lower than 1024 x 768. Annoyingly there is no error or warning message.
Try switching to Windows Desktop App and increase resolution as you would do on any Windows 7 machine.

If you can't increase resolution to at least 1024 x 768, you can try a registry hack suggested here.