Install LW again. It will try to uninstall the previous version. If it can' t do so, then you might need to use CCleaner to remove the rest of the old installation.
http://www.ccleaner.com/download/
Besides, it is anyway a good program to clean up your computer and it's free.....

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"Never Argue With An Idiot. They Will Drag You Down To Their Level, Then Beat You With Experience"