go into the LimeWire folder in your hard drive, and double-click on the lime icon. see if you still see ads. if you don't then you're probably clicking on an alias in your dock or on your desktop that belonged to the freeware version.
if you don't see any ads, but are still being asked to upgrade, go back to the download site and get the most recent version of LW. uninstall the current version, then reinstall.
zbell