i;ve been having some luck with taking a pure sine wave, bout 100hz (made from SoundForge - tools-->synthesis-->simple) and then add some distortion and compression and then what ever else i happen to insert on the channel which makes it sound good :)
the classic hardstyle bass line is a kick drum, played in reverse and then fuked about with - i've never found the right kick drum to use and not really been able to make my own but thats when the joy of sampling comes into play ;)