Do you have the LimeWire program running while doing this? If so the installer can not overwrite the old LimeWire if it is still running. Exit out of LimeWire and wait for it to shut down. Then hold control+alt+delete and wait for the task manager to appear. Once this has occured click on the second tab from the left labeled processes. Once there search for LimeWire. If you find it click it and then click end process at the bottom right of the task manager. Now try to install the new version.