New Windows 7 computer; old network w/4 XPs. W7 can use files on XPs; XPs can access W7 printer and C:\Users\default & Public subfolders; can "see" C drive but can’t open files. Message: "\\Ralphhome\C is not accessible. You might not have permission to use this network resource etc." W7 drives all set as shared, without password; Network Location Awareness on. XPs communicate fine with each other. Changed ownership to myself. Turned off AVG anti-virus. Nothing helps so far. I've tried to read all the relevant posts on this sort of topic today, and tested each suggestion. I'm still desperate. Thanks to all for any help and for your tolerance.