Sandboxie: installation error

[Wisperjack]

Right, im trying to install and play borderlands the pre-sequel on my pc, normally that wouldnt be a problem but my pc has recently encountered connection errors. Ive gotten around this by using sandboxie to run programs through as they seem to connect fine through that, but this is where the problem lies.

I cant install borderlands: the pre-sequel normally since my pc wont connect to the steam servers, so it wont download the data to install, however it will on sandboxie. It installs but when i try and play it, it comes up with a message telling me to install "steam service". However when i accept it just results in the steam bootstrapper hitting the immediate error "failed to add exception for C:\Program Files (x86)\Steam\steam.exe". Help? :c

EDIT: other fully installed games work fine