I thought the way to block a program's internet access was to go to Windows Firewall and block it there, but the program I'm looking for isn't listed. Is there another way?
You are looking for the solution in a right direction, just a few steps up and you'll get it:
(I'm not using an English OS, so my description of menus and items may not be accurate)
1. Click "Advanced Settings" on the left panel of "Windows Firewall".
2. Click the second item on the left panel of the popup window, which should have an icon of a wall and a green arrow.
3. Click "Add a rule" on the right.
4. On the popup dialog box, click "Program" and then "Next".
5. Select the program path you want to block, and then "Next".
6. Select "Block connection", and then "Next".
7. Choose if you want to block this program on domains, on private network or public network, then "Next".
8. Name it as you want, and finish this dialog.
This approach is a bit complicated, but it works. Maybe there are simpler ways to block a program.