I have a home network consisting of two desktop machines connected via LAN and a netbook. One desktop is running Vista Ultimate 64 bit and the other Win 7 Ultimate 64 bit. The netbook is running XP Home. I have shared folders on the Vista machine that after some random amount of time become inaccessible from the XP netbook. The Win 7 machine can still access the drives, but the XP cannot. When I restart the Vista machine, it has fixed the problem all times except 1 (something like 11/12). I have disabled the 3rd party virus software on the Vista machine and the only thing running on the netbook is MS Security Essentials. I can also ping back and forth from each computer. Thank you very much for any help you may be able to offer.