The installer is likely in your Start Up menu and continuing to be ran on start up of your machine. Please remove it from your Start Up menu. You can find details on your Start Up menu configuration here - http://support.microsoft.com/kb/152122

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If you see the following notification after loading Windows, please perform the steps below:

"We are sorry, but you do not have sufficient privileges on your PC to install LastPass. Please as your System Administrator for assistance."

1. Start menu --> Run --> type msconfig and click OK, navigate to the Startup tab and disable LastPass startup items found on this list. 

*On Windows 10, right click the Start button, open Task Manager and go to Start-up tab.

2. Find and delete any LastPass Run Once files on the computer: type  run once in the search bar of the Start menu (you can safely delete all of the LastPass Run Once files found via the search).

Alternative way of finding the startup files: 

1. Enable hidden Windows files:

Windows 8+: Ribbon --> View --> Options --> View --> check 'Show hidden files and folders'.

Windows Vista; Windows 7: Click on the Organize buton in any folder -->  Folder and Search Options --> View --> check 'Show hidden files and folders'.

Windows XP: My Computer --> Tools --> Folder Options --> View --> check 'Show hidden files and folders'.

2. Navigate to the Startup folder and delete the LastPass startup files:

Windows Vista +: C: \ProgramData\Microsoft\Windows\Start Menu\Programs\StartUp

Windows XP: C: \Documents and Settings\All Users\Start Menu\Programs\Startup

Windows 2000: C: \Documents and Settings\All Users\Start Menu\Programs\Startup

Try renaming the following files:

Locate the following file(s):

C: \Program Files (x86)\Common Files\lpuninstall.exe

C: \Program Files\Common Files\lpuninstall.exe

Rename them to be:

C: \Program Files (x86)\Common Files\lpuninstall.exe_renamed

C: \Program Files\Common Files\lpuninstall.exe_renamed

Note: Remove the space between C: and the slash.