User Permissions when Networking from Vista laptop

> I have read the previous postings, the MS Technet notes, etc. and can’t find
> the answer to my networking issue.
>
> I have a home network: 2 desktops with XP Pro and XP Media, one laptop with
> XP Media, and one laptop with Vista Ultimate.
>
> All can access the internet—that isn’t my problem.
>
> All have the same workgroup name, all can see each other on the network.
>
> The problem is that from my desktop I cannot access the “c� drive of my
> Vista laptop.
>
> I get this error message:
> \\laptop\c is not accessible. You might not have permission to use this
> network resource. Contact the administrator of this server if you have access
> permissions. Access denied.
>
> I am the administrator of all the computers.
>
> On the Vista laptop, I have opened up all the security access. All folders,
> including the C drive, show up on the Vista network tree. It is a private
> network. Password protection is off; everything else is on.
>
> When I go to “My computer�, rt click “c�, and do “share�, it is shared. When
> I click “advance share� and go to permissions, I have “everyone� and “guest�
> as having full permissions.
>
> But, if I click on “add�, it only allows “laptop� as the location. It won’t
> let me add any user from outside the laptop.
>
> How I can get permission to access all the folders/files/programs/ etc. on
> my Vista laptop “c� drive from my XP Pro desktop?
>
> I also have the same problem trying to access the Vista laptop
> \\laptop\kathy folder (my user name). I can’t get access to this at all.
>
> Thank you.
>