Are you trying to install using the online or offline installer? Best to use the offline one, people tend to have trouble with the online! Have you checked in your Task Manager to make sure there isn't a version of LW running?
Normally, installing a new version of LW will uninstall the old version. How did you remove the older version? If you used Add/Remove Programs, it may not have uninstalled properly. The correct way to uninstall LW is Start > All Progs > LW > Uninstall
. You may have to use your computer's search to look for LimeWire & delete things that way before installing a new version!