I'm also on 64-bit Windows 7 and, after using the installer linked earlier on this thread at 4share, The device isn't found.
I think we could use a much more thorough version of this step:
"Make sure all drivers are installed (Fastboot drivers are included)"
EDIT:
I got it to work.
What's important to know is that the driver installer you want is right there on the phone when you connect it to the computer, so there's no need to scour the web for one. A D: drive appears when you plug it in, but then disappears 20 seconds later. Make a copy of PTAPC_V1_1_6_0630.msi before it disappears, then install it.
After that, the next time I connected the phone to the computer, it detected a list of things that took a moment to process and retrieve Windows Updates for. Then, it was ready.
Hope that helps. Also, when these instructions say to pull the battery... put it back in, too.