Security for Shares btn WinXPH and VistaHP

I would appreciate help with fixing a sharing problem between a Windows XP
(Home) PC and a Windows Vista (Home Premium) PC.

The desired scenario is to create a share on the Vista PC that gives full
rights to another user on the WinXP PC. FYI, the LAN has no server. It is
strictly a peer network. There are several peers with their own shared
folders in the office. Most, but not all shares, are open to 'Everyone'.

First, I verified that both PCs were configured for the same workgroup.
Second, I successfully created a folder off the root of C:\ on the Vista PC
and shared it.
Third, I successfully mapped a drive on the WinXP pointing to that share.
For testing purposes, from the WinXP I created a new folder; then a new
document. This was successful - at least initially. However, when I
attempted to delete the two objects I just created, I received an 'Access
Denied' and the WinXP system hung. I was forced to manually shutdown the
WinXP PC in order to recover.

The complication seems to be with adding security to the share.
Specifically, I tried to restrict the share to this one other user.
I created a user account on the Vista PC for example 'guestworker'.
I then created a user account on the WinXP PC with the same user id and
password.
I then added 'guestworker' to the share as a co-owner.
When configured with security, we can access the share and read the
contents, but we cannot reliably obtain full control of the files and
folders in the share from the WinXP PC.

Is this a problem with simple security? Should I setup security differently,
for example, restricting the share to just one user, versus unlimited, but
give the user, 'Everyone' full control?

I look forward to receiving your comments/suggestions.