echo problem

When I am in any part of Audacity I get what sounds like 2 tracks of the same song with one delayed by about one second. When I go to record I get the usual blue waveform but it has red waveforms mixed in with it. I have Windows XP Pro and I loaded Audacity from the internet but there is no installer showing in my downloads. I have been using the same method of cassette to digital and it has worked well enough, but now everything is blowing the walls off my sound card. I have lowered the input levels using the Realtek sound manager but I still get all my input from my cassette deck at very high and almost uncontrollable levels. It worked really well until now, and I am using the same method of transfer that I did on the rest my projects, but now the thing is gone haywire. I am plugged into the blue input jack on the back of my PC (HP 5750 Compaq) and all has been well until now.

Open the Transport menu and make sure that “Software Playthrough” is off (not selected).