XP and OmniClient (again)

XP Pro SP 2, RiscPC 4.37 and Iyonix 5.10, both running Omniclient.
Previously Omniclent worked well, allowing read/write operations on PC
from both RISC OS machines. Change occurred after having to install
new hard drive on PC, therefore re-loading XP. This is strictly
speaking an XP problem, but as I am trying to access it using
Omniclient, this post is distantly on-topic.

I seem unable to fully share any directories on the XP. I have focussed
on Documents and Settings, containing the most-used files. No matter
what I try, re-opening its Properties viewer reveals that it is marked
Read Only, having previously unchecked the option. Have tried most
combinations of re-setting permissions in the sub-viewers, and, of
course the Share option, in different sequences, but the read-only
option remains selected, which is reflected in the Full Details view in
Omniclient on both RISC OS machines. The firewall list does not appear
to contain relevant settings, but others may have a more practised
opinion.

My user setting in XP is Administrator.

What should be my next step? - and, yes, I do need my PC until Adobe
writes a RISC OS version of CS2 Premium :-)

.