I have Vista Ultimate on my main machine and XP Pro on my laptop.There is also another machine running Vista Ultimate and another XP Pro laptop in the house. My Vista machine has only one accountand that account has password.The other Vista machine has only one account and that account does not have a password.Password protected sharing is (supposedly) disabled on both machines. Both Vista machines can access each other without needing a password, as you would expect. When either of the two XP Pro laptops attempts to access shares on the Vista machine which has a password set on the local account, a password prompt is displayed. However, entering anything at all into the username box and hitting OK will grant access. When either of the two XP Pro laptops attempts to access shares on the Vista machine which DOES NOT have a password set on the local account, no password prompt is displayed and access is granted immediately. Here's where the odd behaviour starts. I tried to confirm this by setting a local password on the Vista machine which did not have one - but that machine still granted access to shares without prompting for a password even after restarting both that machine and the laptops. However, if I remove the local password on my Vista machine then both laptops can access shares with no password prompt. Setting a local password again brings back the prompt when attempting to access shares. Clearly something has got "out of sync" somehow on my Vista machine. I haven't played with security policies or anything like that, and I first set the password during the install process and until today's troubleshooting attempts I hadn't modified it. To reiterate:There is a single local administrator level account on each Vista machine.Password protected sharing is disabled on both machines in the Network and Sharing Center.XP can access my Vista machine without a password prompt ONLY when my local account does not have a password set.XP can access the other Vista machine regardless of whether the local account has a password set or not. I don't know if there's a security policy setting which has got incorrectly set which I could change, or whether it's something more serious.I could really use some help here, I can't figure it out at all. Thanks!