no sound or waveform (not recording)

Hi
iv recently reinstalled audacity but while recording theirs no sound or waveform (not recording) iv had audacity before but had to wipe everything off my computer because of a virus, the 1st time I had audacity I had no problems and I haven’t changed anything like my mixer or leads or anything, Iv played about with the soundcard settings and its still the same problem.

help needed please

http://manual.audacityteam.org/o/man/faq_recording.html#flatline


Gale