Unless you know you need one of the old versions for compatibility with a specific Java applet, then it's not only okay to delete those old versions, it's actually recommended to get rid of those old versions because they represent a security vulnerability!
What the friend on the other forum told me was that while he wasn't sure if I could delete the old updates, he did know that I could uninstall everything and do a fresh install. That's what I did, and I am quite pleased with the results.