If you upgraded through DM, then the OS has to be installed on your PC. It's impossible to install from your PC using DM without installing the OS on your PC. Look in the Add / Remove programs area again. You should see an entry very much like "BlackBerry Device Software v5.0.0 for the BlackBerry 9630 smartphone." That's the OS you are looking for.
When you downloaded 5.0 to your PC, did you double-click the exe file? That's how you install it. You don't have any control over where it installs, and it can't be installed anywhere else. If you downloaded it, but didn't double-click it, you never installed it to begin with. That would explain why you can't delete it.
DM is trying to install the latest OS from your carrier. You can stop that by disconnecting your PC from the internet while you upgrade top .484. You can double-click the 484 exe, disconnect your PC from the internet, and run the App Loader to install .484.
If you're on a wired network, unplug your network cable. If you're using wifi, turn off the radio. There is usually a hardware switch somewhere on your device that allows you to turn it off.