as already said… NO Security program have 100% detection…
something like 100 000 samples of new malware code is found every day, so it is mission impossible to detect it all…

then i frequently got message saying you got virus in your system so it might cause hard disk crash etc. From Microsoft Firewall.
to me it sounds like you are infected With a Rouge/Fake AV

maybe this one ?

Remove Windows Firewall Unit (Uninstall Guide)
http://www.bleepingcomputer.com/virus-removal/remove-windows-firewall-unit

the removal expert here in the forum will help you remove it if you want…and all help is free