I finally got my Ultranav to complete functionality on my ThinkPad T61 running Windows 7.
Here are the steps I followed.
Download the Ultranav driver for your specific model from the Lenovo support website and install it under Windows Vista Compatibility (Right click on the setup file > Properties > Compatibility). Take note of where it is installed. For me, it was C:/DRIVERS/WIN/UNAV.32
Then go to the Mouse settings in the Control Panel, and to the Hardware tab of the Mouse Properties. Click on Properties button for the shown mouse device (it listed a standard PS/2 mouse). Then click Change Settings on the Device Properties window that opens; go to the Driver tab and click on Update Driver, and choose Browse My Computer for Driver Software. Then browse the file system until you choose the folder that the new driver was installed on. Click OK and Next and it will install the new driver. When it finishes, you need to restart your computer for the changes to take affect. Then the TouchPad scrolling and middle button/TrackPoint scrolling should be functional, and the settings can be changed in the Control Panel.
This is a major convenience, as I'm accustomed to using the TouchPad scrolling for everything.