Have you ensured that the system is set up to allow file sharing? Generally in its default set up vista does not allow file sharing through the firewall. You could try \\127.0.0.1\LSBackup My suspects would be firewall and then authentication. Good luck and please post your solution.
One critical thing you did not mention is the firewall. Like I mentioned, many times Windows Vista does not support file sharing out of the box and it sounds like that is your case. Even if it is the same computer if file sharing is blocked you will have no chance. I am not sure what "restore" means in your message. Are you browsing from explorer to \\hp-pc ? If that is the case then it is certainly not a firewall issue.
If you're strictly test prepping, I wouldnt worry about making the log shipping work as long as you know what it is, and how to do it.