manage to do this on my x64 Windows 7.
key thing is to get the right drivers
I download the drivers from here, http://download.theandroidsoul.com/f...ootloaders.zip
and use the fastboot drivers from the drivers folder.
then in that few seconds where the phone is in fastboot mode, I update the drivers accordingly.
The problem I think is Windows 7 will automatically redirect the driver installation to default/generic installation if it can't find the driver for the device. So perhaps to avoid it totally it's to use gpedit.msc to stop the redirection of the devices..