That might be a bit of a problem. A service account that a web service normally runs under has very limited access to local resourcs, particularly accessing user configuration settings like what you're trying to get to.
Perhaps we should step back a bit and ask why you want to do this. It can't be the end result you're looking for, but something to facilitate something else. What is that something else that you wanted this in order to achieve? Perhaps there's a more straightforward way to do it.