1. Try looking in the add/ remove programs section if not done already.
2. Try installing the game on another partition of your hard disk, if you have partitions on your HDD
3. Use the search tool in windows to manually locate files concerned with Star Wars the Force Unleashed II and delete them manually.
4. Right click on the game disk and then select "explore folder" option. Try running the installer manually. Remember to create a new directory, different from the one in which you previously installed the game.
Try these, if it doesn't work, we'll try something else.