Photoshop Elements: Now that I own Elements 9, can I delete Elements 6?

I recommend that customers just leave the old version there - at least for few months. Disk space is cheap - and you might remember want to go back and look at a preset or something you created in an older version - or a third party plug-in that's compatible with an older version. If after a while you haven't found the need to go back, then go ahead and uninstall or remove it. I forget if Elements 6 has activation, but if it does, make sure you deactivate it before you remove it.