This method worked for me:
http://andrewblock.net/2011/03/07/how-to-uninstal…

1) as i didnt care much about breaking stuff at this computer i started at first to disable the services.

run: windowskey + r > services.msc

and stop and deactivate all symantec services. one of the services can’t be stopped but that doesnt matter. (annoying windows keep popping up later, simply keep closing them.)

2) then i went to the registry and simply whiped out everything that was called “symantec”

run: windowskey +r > regedit

and delete the whole keydirectory HKEY_LOCAL_MACHINE > SOFTWARE > SYMANTEC

(i found out later that this disabled the password prompt, too)

3) then i rebooted using a linux live cd and simply whiped out all symantec files on my hard drive

C:\Program files\Symantec\

C:\Program files\Shared Documents\Symantec Shared\

and reboot back to windows. this did pretty much the job, but the annoying popups still kept coming (symantec was still there after whiping out almost everything)

4) now i was able to stop and deactivate the last symantec services, see 1st step.

5) finally i was able to go to system settings and to uninstall symantec without password.

if some of the steps fail, keep trying and add reboots between them. good luck.

I needed to reinstall a different version of endpoint…