can no longer download .exe or remove Comodo Premium

I’m still on XP SP3.
After updating to Comodo premium (free) I’ve noticed that I can no longer download .exe unless I use a bittorrent client, and even then I can only simulate an installation using sandbox.
I’ve also discovered that Comodo is impossible to remove (on my current level of understanding) regardless of whether I disable it on startup (Ccleaner) or attack it with scrubbing software. I should add that Comodo does not appear on my add/remove programs window.
Are these problems connected? Or is there a simple fix?

Sometimes a clean install can work miracles of course.

When installing a program don’t run the installer in the sandbox. That will not work. Other than with Sandboxie you can’t install programs in the sandbox. Allow the installer when you trust the program and download source.

You should be able to start the uninstaller from the Comodo group in your start menu.