Just wanted to resurrect this thread since I had some of the same problems with my TuneECU cable (a cheap one off amazon) not showing up in my device manager list at all after driver installation, and I'm also using Windows 7 Home Premium 64-bit. Actually the first time I tried to connect something corrupted the ever living shit out of my computer, and I ended up having to wipe my machine clean and re-install the OS. However the first time I did it I did everything wrong, leaving my wi-fi on, letting it install drivers automatically, and trying to start the bike with everything connected. Not sure if it was the drivers or a power spike that screwed me over, but I would recommend doing none of those things.
The installation instructions on the FTDI site showing how to display inactive devices in Device Manager saved me. Did that so the cable showed up greyed out, uninstalled the drivers and re-installed the drivers a couple times a few different ways, and the computer finally recognized it correctly as both a USB Serial Port (Com3) under Ports and as a USB Serial Converter under USB Controllers. There are two different installation files you can choose from on the FTDI site, but the only one I had luck with was the executable in "CDM v2.08.30 WHQL Certified.zip" after it was unzipped and the zip file inside it was also unzipped, not "CDM20830_Setup.exe" even though it's supposed to be the same thing. When I ran it I also had to right-click and select "Run as administrator"; even though I am the administrator on my own computer, apparently this makes a difference, since Bill Gates doesn't trust you with his product. Totally straight forward, right?
I also noticed that my craptop wouldn't recognize the cable if it was plugged into the bike first - even though that's how the TuneECU site says to do it. Instead I had to connect in the following order:
1. Plug the adapter into the laptop. If it doesn't show up as a Com3 port, unplug it and keep messing with the drivers until it does.
2. Power on the bike (not necessary to start it though)
3. Start the TuneECU application
4. Plug the adapter into the bike
5. Select Connect in TuneECU, in case auto-connect isn't already selected (I think it'll work either way though)
6. Load an awesome map
7. Braaaap!