Update

I have not received any further replies with helping suggestions and so
meanwhile
I have been trying to fix this virtually non stop over the last couple of
days. Earlier today I tried sharing the c drive of the laptop (WinXPpro
machine) which said the computer was not setup for networking & prompted me
to run Network setup wizard! I have no idea why this would be but anyway I
ran the wizard (which was in effect a rerun as I had already done this from
the control panel>networking ).Still no improvement. Throughout all this the
laptop was rebooted from time to time. I then re ran the network
troubleshooter which as step1 said try logging off & logging back on which I
had not done before when using the troubleshooter because throughout all of
this I had rebooted several times and logged in with still no improvement.
However this time I did log off & on again as the troubleshooter advised in
step1 and had some limited success as I was able to access a share folder and
view and edit the files therein! So some progress was finally happening!

It took some further time to make a share to the folder on the hostXphome
computer that I really needed access to, but I have managed to acheive that.
Many other folders on the XPhome host though remain inaccessible with the
access denied message still occurring (even though they are enabled for
sharing!).

So really I have no idea why this hasn't worked fully smoothly but finally I
can access a folder I need to & read & write to from either computer on this
wireless  so I have to leave it there for now as I have spent days trying to
get this networking right. Whatever was the problem? I followed all
instructions correctly & time after time with no result until now this
limited one! (This leaves me tired & frustrated with computing & Microsoft
Windows!!Do Microsoft know that problems like this occur?Hopefully now I can
get back to work!- also I have just installed Avast virus software so hope
this will work ok.....time will tell I guess).

I know other people have had these problems and if anyone still has such a
networking problem I can only offer goodluck and advise to keep trying! Not
much help I know but it may just fix itself mysteriously like my problem
seems to have done(& if I take any more time I might try to access more
folders but not just now!).

Happy computing & best wishes to all