If
NullSessionPipes is correct and you still have trouble check other phrases in key
HKLM\System\CurrentControlSet\Services\LanmanServer\Parameters ->my image in post 2.If other phrases you have OK also,try to install SP2 for Vista from Microsoft Download Center (if you don't have SP1 you have to install it before)
Download available for Standalone Vista SP2
FYI
When you install SP2 you don't need install Windows Installer because the newest version is already included in SP2
And no more idea