Take my advice and move the security up a notch as well as possibly solve the issue.

Forget Windows based network sharing and move to SSH with http://www.openssh.org Both servers and clients are available and very secure.

What you don't want to know is that the Read-Only sharing in Windows has been compromised far too many times in recent history. Moving to OpenSSH will cure this and help in that your friend's machine will not auto-infect your machine when the next worm/device comes out.

Look at WinSCP if a person doesn't want a command-line.
Look at PUTTY if a person wants a command-line set.

Bob