Go to "run" type msconfig. That brings system configuration, click "boot" then select the operating system to be delected. Enter a check mark in "make all boot settings permanent" click "ok" then "apply". Bang you done
How do I uninstall duplicate vista operating system.
Do you actually have a dual Vista boot at startup ( that you can actually boot to 2 versions), or do you mean you have a folder "Windows.old" from a previous instalation that you want to remove, the process is different for the two choices.