Why is iTunes a hot mess?

Put a new hard drive in my computer last winter. Reinstalled my backup. Reinstalled my software, including iTunes. Went to route my audio files through iTunes and it froze EVERYTHING. I attempted multiple times to uninstall it and start over, but with each new re-install, it immediately picked up the process that froze the computer before (without being told to do so) and froze my computer. I gave up and used sub-par, 3rd party apps for syncing and ripping. Now 8 months later I tried to install iTunes again but it's still installing anew but picking up that 8-month old process and still freezing or freezing my computer. Any ideas what's going on or if I can fix this?