You need to go to your Control Panel and open the Java Control Panel. Click on the Java tab and press the View. You will see what Java versions you have installed. Disable Java 7 and make sure Java 6 is checked.

To find the LW preferences folder. Go to Start menu, type LimeWire into the search box. You should see a LimeWire folder listed under files. Hover your cursor over-top of the specific listing and it should specify the location. C\Users\your account name\Administrator\AppData\Roaming
If you do not see it listed, click the Files name to see more results. If it is not any of those then you will need to change your view settings to find it unfortunately, even if only temporarily.

I am mainly a Mac user, maybe a Windows user has a better explanation or technique to find a file or folder that is inside a hidden folder.
This is the only way I know. To change the options of viewing files and folders via the Organise menu. If you find the folder in question, right-click and send to Recycle Bin. If you had incomplete files, you could return the Downloads file from the recycle bin back into the new LW prefs folder after your first session of using LW again.