The following two commands are recommended per this article for disabling SMB2 on Vista, Windows 7, SBS 2008.
sc config lanmanworkstation depend= bowser/mrxsmb10/nsi
sc config mrxsmb20 start= disabled
(Please note that there is a space immediately after the = sign in both commands!)
If you have several Windows 7 workstations, then check out this article for pushing out the above commands via PowerShell.