Your entries for the Windows 8 hackathon should be built with the RTM version of Visual Studio running on the RTM version of Windows 8. A 90 day free trial can be downloaded. If you're a MSDN or TechNet subscriber, you can use download the RTM version there.
If you built on Release Preview and need more time to install RTM, then you should submit your Release Preview version and then send me a private message here.
