I've managed to get this to work fine on Windows 7 64-bit (I have a Dell XPS Gen 2). It took me a while, but I managed to get the driver file (fanio.sys) signed using the Driver Signature Enforcement Overrider. I believe the driver file is now permanently signed and can be installed on any 64-bit system (not just mine), but I haven't been able to test this out.
I've posted my modified copy here:http://www.acaeum.com/images/I8kfanGUI64.zip
Please try it out and let me know if it works. Note the "readme.txt" included in the distro -- I had to extract the files from the installer in order to sign the driver, so you have to manually install this now. Simply copy all the files to your Program Files x86 directory, then run the "faninst.exe" file to install the driver. Run I8kfanGUI.exe directly after the driver's installed.