Can I get rid of three year old Windows security updates and how?
Some details would be nice....ya think?????
Your method is entirely too dangerous and deviates from the OP's original question. Based on the description, he needs to remove an update, not conserve space after an update.
What update is it? You can usually remove any Windows update, no matter when you installed it by going to Start -> Control Panel -> Programs & Features -> View installed updates -> Remove the update
Make sure you create a backup before you do so! Also be sure that when you check for updates next time, that you don't re-install it.