Open task manager (ctrl-alt-del) & check whether there's a LW process running. If there is, end the process. How did you uninstall the original LW? If you uninstalled via add/remove programs, that can cause problems. You might have to use your computer's search to look for all LimeWire files & folders, then delete from there.

The correct way to uninstall LW is via start > programs > LW > use the uninstall option Installing a new version of LW will also automatically remove the old version.