Windows 7 Browsing Network

OK, so having turned off local master, preferred master and set OS level to 20. I now have browsing working, with anoth machine taking the role of local master.

Whenever I set the NAS / Samba to be local and preferred with OS level set at 255, it loses the election to a win 7 PC. It cycles through being the browser and then losing it frequenty, around every 20 seconds (it wins and then loses)

I've just left it off and will allow the win 7 PC to be the master.

There doesn't seem to be a way to make the NAS be the master:

Exert of settings:

[global]
 allow trusted domains = 1
 delete readonly = 1
 dos charset = CP437
 encrypt passwords = 1
 follow symlinks = 1
 guest account = nobody
 hostname lookups = 0
 idmap gid = 35000-65000
 idmap uid = 35000-65000
 invalid users = root
 load printers = 1
 local master = 0
 log level = 0 auth:2
 map acl inherit = 1
 map to guest = Bad User
 max log size = 256
 name resolve order = "lmhosts host wins bcast"
 null passwords = 1
 obey pam restrictions = 1
 oplocks = 0
 os level = 20
 passdb backend = tdbsam
 passwd program = "/usr/bin/passwd %u"
 preferred master = 0
 preserve case = 1
 security = user
 server string = %h
 short preserve case = 1
 socket options = TCP_NODELAY SO_KEEPALIVE SO_SNDBUF=262144 SO_RCVBUF=262144
 store dos attributes = 1
 syslog = 0
 syslog only = 0
 template homedir = /c/home/%U
 unix charset = UTF-8
 unix password sync = 1
 veto files = "/TheVolumeSettingsFolder/TheFindByContentFolder/Network Trash Folder/Temporary Items/"
 wins server =
 wins support = 1
 workgroup = PANET