So apparently the guide needs a bit of a re-write for Windows 7, here is what worked for me.
1. Start -> Search for “hdwwiz” and Run it.
2. The wizard typically displays a screen explaining what it is used for. Click Next to continue.
3. The wizard may automatically scan for new hardware. The scanning will not detect anything related to PortIO32.
4. You will be asked whether Windows should search for the new hardware. Select “Install the hardware that I manually select from a list”
5. A list of hardware categories will be shown. Select “Show All Devices” (On some versions of Windows this may be called “Other”)
6. Click the “Have Disk” button and point Windows to the “win\driver” directory of the PortIO32 distribution.
7. A list of drivers found in the directory you specified will be shown. Select the “PortIO32 Xbox 360 Device Driver” item and click Next.
8. Click Next again to “start installing your new hardware.”
9. The files will be copied and installed. Click Finish to complete. You do not need to restart your computer.