You're going to want to change the HiddenServiceDir line, so it -points to an actual directory that you have read/write access to. Fill -in your own username in place of "username". For -example, in Windows you might pick:
+points to an actual directory that is readable/writeable by the user that +will be running Tor. For example, if you're using the OS X Tor package, +you might pick: ++HiddenServiceDir /Library/Tor/var/lib/tor/hidden_service/ +HiddenServicePort 80 www.google.com:80 ++
On Unix, try "/home/username/hidserv/" and fill in your own username +in place of "username". On Windows you might pick:
HiddenServiceDir C:\Documents and Settings\username\Application Data\hidden_service\ HiddenServicePort 80 www.google.com:80