i have created a small tool that will allow you to use Dexcom Studio on Windows 8 to sync with the G4 receiver.
Please be aware that this tool is not supported by Dexcom - i was just frustrated with the lack of official support for Windows 8 and tried to make it work somehow. On another thread this tool was tested by several people - and improved in multiple iterations thanks to their real world feedback.
So if you want to give it a shot despite the lack of official support from Dexcom, just follow the installation steps below. Feel free to contact me if you run into any issues.
The tool is located here: http://sdrv.ms/YUEqzr
1) Download and unzip InstallDexcomWorkaround.zip to your machine
2) Connect your G4 receiver.
3) Start InstallDexcomWorkaround.exe (for example just with a double-click)
4) The program will ask you for permission to run as an Administrator
5) The tool will report the status and the apply a workaround to the regsitry so that Dexcom Studio recognizes your receiver.
You don't have to re-run this tool each time you want to start Dexcom Studio - only if you attach your receiver to a different USB-port.