File sharing: Can't access folder when desktop is locked....

I like to have my desktop PC at home set to show the welcome screen when the
screen saver comes on. To log back into Windows, you have to enter your
password.

I have a simple wireless network that includes a desktop PC upstairs,
running Vista, and a laptop that is usually downstairs running XP. When I
had XP on both machines, I could access shared folders from the laptop that
were located on the desktop as long as somebody was logged into Windows on
the desktop machine. It did not matter if it was locked by virtue of the
screen saver activation.

With Vista, I cannot access shared folders when the desktop is locked
without entering a username and password. This is annoying and I don't know
where to go to fix this problem. The intent of locking the desktop once the
screen saver kicks in is to prevent someone from else from getting to my
personal files, not prohibit access to shared folders.

I have set the file sharing options as follows:
Network discovery: On
File Sharing: On
Public folder sharing: On (read only)
Printer sharing: On
Password protected sharing: Off
Media sharing: Off

Could somebody tell me if there is a way to get it back to how it was with
XP? If I have to leave myself logged into the desktop without enabling the
"On resume display logon screen" option (thereby allowing anyone to access
all of my personal files) in order to allow access to freely shared folders,
then I'll just go back to XP. But hopefully I'm just not finding the setting
to turn that feature off.

Thank you in advance.