You can have problems if try to uninstall LW using Add/Remove Programs. The way to uninstall is Start > All Programs > click on LW & choose the uninstall option.
Normally, installing a new version will automatically uninstall the old as well. Go into Task Manager & see if LW is running, if it is then end the process. Now see if the new version will install properly. If not, you might have to use the computer's search & delete all the LW files individually... then install the new version