Vista - XP to Vista sharing problem

JFYI of anyone reading this:

I installed, about 2 months ago, a new computer with Vista Business on it at
an accountancy practice. The moment that I connected the cable, it found the
ADSL modem router and asked if this were a private, work, public place so I
said Work and then allowed IP via DHCP to get it on the network. All shares
could be seen by the Vista machine and all could be accessed by it. The rest
of the machines on the network were all XPSP2 machines. I go to one of them
and all is OK all working and same with each one in succession. Job done, I
go away. 2 days ago, lots of complaints from one of the company's owners
about not able to do a thing with the new machine. He fancies himself "tech
guy" with super cape and underwear on the outside and a big S on the shirt
somewhere....my guess is he forgot the "H.I.T." after the "S".

Anyway, he had fooled with everything and one XP machine would talk to
anybody or anything, 2 were OK and the Vista machine refused to look at the
network at all. XP machine was easily fixed but Vista wasn't. I have never
encountered this problem before:

Vista machine wouldn't see network but WOULD see internet through the same
ADSL router as was there when first set up *BUT* network name was the same
on all machines and all were getting IP addresses from the same router thus
subnet masks were all the same. Some fiddling later - eg, star from scratch
on Vista machine - it was seeing and accessing XP shares on those machines
but though they could see it, they couldn't get to it and nothing was
changing that. I gave up at that point and created the same username and
password on the XP machines as is on the Vista machine. I also changed the
Vista machine to require username and password to access its shares. I still
couldn't get on to them. Frustrated at this inconsistency as it is really
only simple networking, I decided to do something I don't normally do and
try to map a network drive - the C on the Vista machine - from one of the XP
machines. The moment I did that, all shares opened up on every single
machine to the Vista machine and all worked as they should. I deleted the
mapped drive to see what would become of the shares, rebooted all machines
and it continued to work and does even now, some days later. It makes no
sense.

Anyway, it was yet another thing to remember for all of you attempting to
get XP to Vista networking going and cannot. Put the same username and
password on the XP machines as is being used as the main account on the
Vista one then from an XP machine, try to map a network drive as I did and
see if it helps. I cannot account for why this should work. I can only say
that it cleared all the rubbish up and made every machine talk to each other
both ways.

Hope this helps some of you.