Can I uninstall Windows 8 Consumer Preview?
No. To go back to your previous version of Windows, you'll need to reinstall it from the recovery or installation media that came with your PC.
"Is there a workaround?" you ask with a twinkle of hope in your voice. No, it appears there is not. If you have the recovery discs or an image of your system, you might be in luck. If you boot from Windows 7 you will notice that the windows 8 preview cannot be upgraded to Windows 7. You would need to do a clean install. Maybe you search for a restore point, but you didn't make one..