Question: I don't want ACT to run 64-bit, how can I change this?
There are some reasons to avoid 64-bit, mostly having to do with native code plugins that don't have any 64-bit support.
On new installations, there is a Start Menu shortcut to run ACT as 32-bit only. On old installations that updated to 64-bit, you may have to create your own shortcut pointing to "ACTx86.exe". Look at the Properties of your old shortcut for your installation folder; using Find Target or Open File Location.
Because ACTx86.exe is a different file name, running ACT like this will cause it to look for ACTx86.config.xml to store configuration settings. The first time you run ACTx86, you will be starting fresh due to the missing configuration file. If you wish to import your old settings, go to the Options tab, Configuration Import/Export section and click the Import button at the top. By default, the open file dialog will bring you to ACT's application data folder. Look in the Config sub-folder for "Advanced Combat Tracker.config.xml" and import that.