Vista - driving me mad

New to Vista.
Thanks to help from Mick I have successfully networked this new computer
(Vista) with my XP computers.
Specifically, I have shared 2 partitions and 1 folder on the Vista computer
giving unrestricted access.
These appear on the XP Pro computer I'm using at this moment.
However, every attempt to open these shares fails. The undernoted is message
from attempt to open the only folder within partition D:

"\\G33\Program Files 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.
Access is denied

OK"

PS I have just shared the DVD drive on the Vista computer and the XP
computer can open without trouble.

I confirm the Vista partitions and folder are open to "everyone".

Hlep