Windows 7: Workgroup vanishes

Its like magic, really annoying unfunny unwanted magic.

On a fresh install - no probs, the 4 other XP boxes in my lan pop up in explorer. Lovely.
Im behind an IPcop fire wall so I dispense with all MS firewalls on all machines, disable the appropriate services and run AVG free with the usual Malwarebytes and a few other freeware/open source tools accasionally.

And I also dispense with the whole Windows 7 HomeGroup bizzo

Then.... my workgroup vanishes in explorer !! I can still map drives and connect though. So I did a reinstall thinking I had screwed up... network pcs there, then a few days later... not there.

Applied this* regedit workaround and I get my workgroup back.

******
HKEY_LOCAL_MACHINEE\System\CurrentControlSet\Control\Lsa\



1. On the right side find ‘everyoneincludesanonymous’; change the value to 1
2. Find ‘NoLmHash’ and change the value to 0

MACHINE\System\CurrentControlSet\Services\LanManServer\Parameters à ‘restrictnullsessaccess’; change the value to 0
Close the registry editor and restart the computer.
**********

THAT Worked fine for a week or so... workgroup gone AGAIN.
Can still map drives no prob.
"re-applied" above regedit - NO JOY

Whata pain in the ass !!

Any pointers GREATLY appreciated.