I have been able to connect to my XP machines from Finder in OS X 10.6.4 with no problem for months. Now I'm getting strange errors. First, when I attempt to connect to server0, I get a connection failed error. Then I click on "Connect As" and a login dialog comes up with the registered users name filled in with mbp17 and a password pre-filled in. The "remember this password in my keychain" is checked. I went into the Keychain.app and deleted the passwords listed for the servers (my 3 XP PCs). Also, there is no mbp17 user, as I deleted that from my server0 several days ago. What I'd like to know is where is the login dialog getting the mbp17 value for the name field, and how can I get rid of it. I'm assuming the other errors are XP related, but I want to get rid of the default values being filled in on the dialog box. Please help.

Check Home>Library>Recent Servers

There is no Home directory on my system, only an alias to /. There is, however, a /Library directory, but it doesn't contain a Recent Servers directory. There is no Recent Servers directory anywhere on the system, so I'm not sure what you're asking me to do..

On the Mac, in the menu at the top, Click and hold on Go.
A pull down menu will appear. Move the mouse arrow to Home.
A window will open. You are now in your Home folder - aka you user folder.
Now in the View menu select by list.
Now locate and open the folder Library.
Recent Servers folder should be there.

You can also try -
Using the Go menu select Connect to Server.
A new window will open. Click on the Browse button.
The Network pane will open.
You can delete the files from there.

That's what I thought, but there is no "Recent Servers" subdirectory anywhere on my system.

Go back into Keychain Access and double check the list of All Items under login.

If there is nothing left, then I am stumped.

You're stumped :)
That's one of the first things I tried.

Are the PC XP on SP3? Plus read this MacWindows reader tip (http://www.macwindows.com/Fix-Mac-Win-as-non-guest.html) for connect 10.6.x to XP, it might help.