How can we do this in CF?
For CF to be able to do it, you have to be able to do it from the server. IF you can log in to the ColdFusion server, and from that server go to 'Network Locations" and browse to a clients computer. Then ColdFusion can do this, using the same UNC path you used in Network Locations. This might be possible on a local network which one might have at some company or other oranizations.
But CF can NOT see what is on the client machine through HTTP. First of all, ColdFusion is not even talking to the client, the web server (IIS or Apache) is what talks the client. ColdFusion is talking to the web server. Secondly the HTTP protocol is designed to prevent exactly this type of interaction for security reasons. IF one could do what you want to do with HTTP, it would be trivially easy for evil programmers to make web sites that trick users to upload all types of sensetive information.