about different firewall tests....

know there are many different firewall testers out there, but one thing ive been curious about...when i do the sygate tests at sygatetec.com, and grc.com it says all the ports it scans are stealthed, but sometimes when i do the testing at pcflank.com all the ports are stealthed except ports 134,135,137,138, and 139. Those ports always show up as visible for some reason. Pcflank.com is the only tester site where those ports are visible, the other sites i goto stated above says all ports are stealthed. So i was wondering whats wrong and if the test at pcflank.com is not as good as the tests on grc.com........these are the firewall testing sites i use http://www.testmyspeed.com/firewalls/scan.htm http://grc.com/ im just trying to make my computer as "hackerproof" as possible