Note that to get the 9.5 version, you must download the “legacy” version from the TradeStation download page, which is below the option to download TradeStation 10.
Also, if you do decide to upgrade from 9.5 to 10, make sure to keep a copy of your workspaces and desktops, as once they’re upgraded to 10, we’ve found that it’s not simple to go back to 9.5 unless you have a backup. If you don’t have a backup version and you want to go back to 9.5, you may have to manually recreate them.
You can install both TradeStation 9.5 and TradeStation 10 on the same machine, though you can’t run both at the same time. When you switch between versions, TradeStation will notify you that it’s making system adjustments that tie everything to the version that you’re currently running. It just takes a minute or so, but it does seem to want to pick one version as the default version. This configuration change only happens when you change versions, so it won’t happen when you run the same version repeatedly.