Go to www.grc.com and follow the link to Shields Up, which offers several choices to check your PC's security.
Here's a direct link to Shields Up (IMO it's the best) - https://www.grc.com/x/ne.dll?bh0bkyd2 As well Sygate has SOS which has a few Different tests - http://scan.sygate.com/prequickscan.html BlackCode also has a nice test, but it takes more than a few minutes - http://www.blackcode.com/scan/index.php
a² Online-Check > http://onlinecheck.emsisoft.com/en/ symantec security check (ie only; activex) > http://www.symantec.com/cgi-bin/securitycheck.cgi
Another good scanner which is supposed to be good , especially on slow scans , is at : http://www.dslreports.com/scan ; However you need to check it out since with me the results have come out to be somewhat inconclusive.
Try this: http://www.firewallleaktester.com/tests.htm In the comparison table, you can find some really good leak attack programs which can REALLY test your firewalls. Sometimes tests provide in vendor's websites and some magazine websites and ww.grc.com are too basic. They can't really test your power of firewall. Use the above. You may find you cannot pass half fo them. If it is really the case, consider adding some system baseline protection like: - processguard(easy to use, not powerful) or - system safety monitor / viguard (require more learning, but more powerful) - registry protection (you may try regdefend but I don't know if it is good)