Journal: Auto-Update Roluette??

I support/maintain a Library Database for the School District in which I live. As of now all my nodes are NT, going on 5 years old, and are a royal pain in the a#% when it comes to applying security patches. This summer however, I plan to replace the aging paperweights with new machines running XP Pro. My question is how do other slashdotters test and deploy secutiry patches when specialized software could be affected, and there is no time to test the patch before the big worm hits. Do I simply enable automatic update for once a week and cross my fingers? (No, using Mac or Linux is not an option!)