Sharing a folder: "...syntax is incorrect."

Just installed Vista Ultimate on my Desktop and Laptop, two existing units
where sharing worked fine with XP.

Now, when I attempt to share a folder from my Desktop on the network, my
Laptop will see the existence of it but can't access it:

"\\Desktop\Folder is not accessible. You might not have permission to use
this network resource. Contact the administrator of this server to find out
if you have access permissions. The filename, directory name, or volume
label syntax is incorrect."

In short, I appear to be "sharing wrong", but I can't see what there is to
do wrong. I'm not trying to limit access to this folder; I want to open it
up for general network access, as I had in XP. I'm not using passwords on
either the Desktop or the Laptop, as it's just me here and I don't want to
log in to each system every time. In light of that, I've turned on File
Sharing, and turned off Password Protected Sharing.

Further: I can't even open the folder as a shared resource from the very
Desktop on which it resides. That is, I can get to it when I just browse and
drill down into the folder from Computer (f.k.a. My Computer). However, when
I go further over on the tree and go down through Network, I'm disallowed
access to that same folder.

Further: When at the "Network and Sharing Center" on the PC where the share
resides, if I click on "Show me all the files and folders I am sharing", I get
no items returned in that search. Once again, though, sitting right there
in the directory tree is the folder, it's icon modified to show that it's
Shared.

Please help me to see what I'm missing. Many thanks!

--Jeff