The checked box on " use Default settings" is grey'd out, as is the "settings" button.

I would like to know some information about this issue, so that we could assist you further.
1. What is the make and model number of the computer?
2. Were you able to install the Touchpad drivers successfully on your computer?
3. Do you get any error code or error message when you open settings?

I would suggest you to try re-installing the Touchpad drivers in Clean Boot state and check if the issue persists. Usually this issue is caused because any third party program that is blocking the computer to change the touchpad settings. Clean Boot will help you determine which third party program or app is causing this issue.

Step 1: Uninstall the touchpad drivers from Device Manager.
a. Press Windows + X keys and click on Control Panel.
b. Make sure View by Category is selected, and click Uninstall a program.
c. Select ETDWare PS/2-XXX, and click Uninstall or Uninstall/Change.
d. Follow the instructions on the screen to complete uninstallation and restart the computer.

Step 2: Place the computer in Clean Boot state.
How to troubleshoot a problem by performing a clean boot in Windows Vista or in Windows 7:
http://support.microsoft.com/kb/929135
Note: After clean boot troubleshooting step, refer to the section "How to reset the computer to start as usual after troubleshooting with clean boot" in the provided link to return your computer to Normal startup mode.

Step 3: Install the touchpad drivers that you have downloaded from the computer manufacturer's website.